The mother of Austin Tice, an American journalist abducted in Syria, said on Monday that she had met with Syria’s new leader in Damascus and expressed hope that “a page will be turned” in the more than decade-long search for her son.

Debra Tice gave a news conference in Damascus on Monday after the meeting with Ahmed al-Shara, whose rebel group Hayat Tahrir al-Sham led the sudden offensive last month that toppled President Bashar al-Assad, ending more than 50 years of Assad family rule in Syria. Syria’s state news agency also reported on the meeting, posting pictures of her in conversation with Mr. al-Shara at the presidential palace.

Although she had no new information on her son’s whereabouts, Ms. Tice, who arrived in Damascus on Saturday, said she felt optimistic that Syria’s new rebel leaders would help her and Syrian families searching for loved ones still missing after being held in the old regime’s notorious prisons.

“It was so wonderful to learn that they are dedicated and determined to bring home my son and your sons,” Ms. Tice said, addressing Syrians searching for missing loved ones as well. “They know what we are going through.”

Ms. Tice said that as far as she knew, her son was still being held captive, but the turmoil since Mr. al-Assad’s ouster made it much more difficult to ascertain his whereabouts.

“It’s like starting all over again,” she said.

Mr. Tice was kidnapped at a checkpoint in a suburb of Damascus in 2012. He appeared not long after in a video, blindfolded and held by masked men with assault rifles. Former U.S. officials said they believed that the video was a ploy by the government to blame rebels for his disappearance.

Former and current U.S. officials have said they believe Mr. Tice managed to escape several weeks after his capture through a window of a prison cell, but was caught by Syrian intelligence.

President Joe Biden said in December, after Mr. al-Assad’s ouster, that U.S. officials believed Mr. Tice was still being held captive and hoped to bring him home, while adding that they had “no direct evidence” about his status.

Officials in his administration spent years looking for Mr. Tice, including a visit to Damascus in December by his special envoy on hostages. The White House also gave the rebel group a list of former Syrian officials who might have knowledge about Mr. Tice, a freelance journalist from Houston who wrote for The Washington Post and other outlets.

But Ms. Tice has recently been critical of the Biden administration, saying it did not negotiate hard enough for her son’s release.

Ms. Tice said she felt hopeful about the incoming administration of Donald Trump. “Things are going to change,” she said. “I’m looking forward to that. His people have already reached out to me.”

It was Ms. Tice’s first visit to Syria since 2015, when she met with officials of the Assad government, who never confirmed whether they held her son and later stopped issuing her visas.

During her meeting with Mr. al-Shara, Ms. Tice said, he spoke to her of his own time in prison. In 2003, Mr. al-Shara joined Al Qaeda to fight the U.S. occupation of Iraq, where Mr. Tice once served as a Marine. Mr. al-Shara spent years in a U.S. prison in Iraq, according to Arab media accounts.

After leading Al Qaeda’s Syrian branch in the early days of the 13-year rebellion against Mr. al-Assad, Mr. al-Sharaa reformulated the group as Hayat Tahrir al-Sham in 2017 and has sought to distance it from its Al Qaeda past.

Former and current U.S. officials have said they believe Mr. Tice was held in several security-service detention facilities, including Branch 248 and Branch 215, both believed to be military intelligence sites.

During her visit to Syria she visited both places, Ms. Tice said, describing them as an “awful, terrible nightmare.”

In the weeks before he took office, Donald J. Trump repeatedly vowed to carry out the largest deportations in U.S. history and to militarize the border, all while his transition team rebuffed requests from regional leaders to meet over the effects of his promised moves.

He made countries such as Mexico targets of his attacks, claiming migrants were flooding the United States with fentanyl and threatening to enforce devastating tariffs. He also zeroed in on Panama, repeatedly asserting that the country had permitted China to take control, compelling the United States to intervene and reclaim the Panama Canal.

So as Mr. Trump was inaugurated in Washington on Monday, the typical congratulatory messages were also accompanied by some from Latin American leaders that deviated sharply from the usual diplomatic norms.

“There is no reason why Mexico should keep its head down or feel lesser than. We are a great country, a cultural power,” said President Claudia Sheinbaum during her daily morning news conference. “Our relationship with the United States will be one of equals.”

She also tried to reassure unauthorized Mexicans living in the United States who might face removal. “Mexicans are very important to the U.S. economy, and the Trump administration knows it,” Ms. Sheinbaum said. “To our countrymen and women: You are not alone, and you must remain calm.”

Mexico is the country with the highest number of undocumented immigrants in the United States, with around four million Mexicans living there without authorization as of 2022, according to the Pew Research Center.

Mexico’s foreign minister, Juan Ramón de la Fuente, also said on Monday that Mexico would not support the anticipated move to reinstate a policy known as Remain in Mexico, which under the first Trump presidency forced migrants applying for asylum to wait in Mexico until the time of their hearings in immigration court. The policy was a boon for drug cartel members, who targeted asylum seekers to extort, kidnap and rape them, human rights groups say.

“Yes, they can do it; it is their right,” Mr. de la Fuente said of the United States. But while allowing that “some agreements” could be reached, he pointed out that Mexico had no legal obligation to process migrants’ asylum requests for the United States.

Hours later, in a message on social media, Ms. Sheinbaum congratulated Mr. Trump. “As neighbors and trading partners, dialogue, respect and cooperation will always be the symbol of our relationship,” she wrote.

But during a marathon session of signing executive orders, Mr. Trump said Monday that he would slap 25 percent tariffs on Mexico and Canada on Feb. 1, accusing both countries, as he has in the past, of allowing undocumented immigrants and fentanyl into the United States. Ms. Sheinbaum and some of her administration officials have previously said Mexico would have to hit back on the United States with their own tariffs.

Following Mr. Trump’s inauguration, the president of Honduras, Xiomara Castro, who warned earlier this month that she was prepared to expel the U.S. military from the country if Mr. Trump pursued mass deportations, limited herself to sending a polite message welcoming him back into office.

But the country’s deputy foreign minister, Tony García, said in a telephone interview on Monday afternoon that his country and several of its neighbors did not plan to accept large numbers of flights carrying deportees without first negotiating the process with the incoming administration.

“They can’t be done unilaterally,” he said, of mass deportations.

Mr. García said that while there are currently no plans to end Honduras’s military agreement with the United States, which permits U.S. operations from a large military base, the Castro administration is still considering it as a potential option, so “they take us more seriously.”

The foreign ministers of several countries met last week to discuss their response to the incoming Trump administration in Mexico City, including Belize, Brazil, Colombia, Cuba, El Salvador, Guatemala, Haiti, Honduras, Mexico and Venezuela. According to Mr. García, the countries agreed that they would not “allow anyone to be deported by force. If a country says no one can come in, not one plane can touch down.”

Honduras is estimated to have about 525,000 unauthorized immigrants living in the United States, according to the Pew Research Center. Mr. García said it had received flights carrying more than half a million deportees from the United States in the last decade. He said the country planned to continue receiving such flights, but the two governments had to work out a plan first.

“We are in favor of coordination,” he said. “Not subordination.”

His were some of the sharpest words for the new president.

In Panama, a target of Mr. Trump’s recent criticisms, including his false claims that China controls the Panama Canal and that the United States should take it back, President José Raúl Mulino roundly rejected the president’s assertions, which he repeated during his inaugural speech.

“The Canal is and will continue to belong to Panama and its administration will continue to be under Panamanian control,” Mr. Mulino said in a statement posted on X.

However, later in the day, the Panamanian comptroller’s office announced that auditors had visited the county’s maritime authorities to initiate an audit of Panama Ports Company, a Hutchison Ports Holding subsidiary. The company is a major ports operator and the country’s main port concessionaire. It is also part of CK Hutchison Holdings, a Hong Kong-based conglomerate.

“The purpose of this exhaustive audit is to ensure the efficient and transparent use of public resources,” the comptroller’s office said.

Mr. Trump’s inaugural address — in which he said he would “repel the disastrous invasion of our country” — frequently took aim at the region, as did many of the executive orders he signed Monday night.

But some leaders reaffirmed their intention to work with the new president and support his policy goals.

President Nayib Bukele of El Salvador, who has close ties to Mr. Trump and his family, was invited to the inauguration but did not attend, said Cindy Portal, a Salvadoran senior foreign ministry official, in a radio interview. Instead, the country was represented by its ambassador to the United States.

Ms. Portal didn’t mention any plans to push back again deportations of Salvadorans, which also make up one of the largest groups of unauthorized immigrants in the country. El Salvador had 750,000 unauthorized immigrants living in the United States in 2022, according to the Pew Research Center.

Instead, Ms. Portal emphasized the Bukele administration’s ties both to Mr. Trump’s son and Marco Rubio, Mr. Trump’s secretary of state, who was confirmed Monday night.

“The message we’re giving Salvadorans as the government of El Salvador is to wait and not get ahead of ourselves,” she said. “President Trump has been clear about returning bad people who went in to destroy.”

She said if Salvadorans have not committed a crime in the United States, they have nothing to fear.

Countries in the region that have been economically isolated by U.S. sanctions had a variety of responses to Mr. Trump’s return to power and his flurry of orders. Nicaragua’s government remained silent, while Venezuela’s interior minister wished Mr. Trump “the best.”

Cuba’s President Miguel Díaz-Canel denounced “the fraudulent designation of Cuba as a state sponsor of terrorism,” in a message on social media. “The result of the extreme economic siege measures imposed by Trump has been to provoke shortages among our people and a significant increase in the migratory flow from Cuba to the United States,” the statement said.

But, in a shift, countries that have been close trading partners of the United States also saw their economies menaced. By late Monday, Mexican leaders had not yet responded to Mr. Trump’s tariffs threat. But Canada’s finance minister, Dominic LeBlanc, did.

“Our country is absolutely ready to respond to any one of these scenarios,” Mr. LeBlanc said. “We still continue to believe that it would be a mistake.”

Reporting was contributed by Simon Romero, James Wagner and Yubelka Mendoza from Mexico City; Matina Stevis-Gridneff from Toronto; Genevieve Glatsky from Bogotá, Colombia; Mary Triny Zea from Panama City; Gabriel Labrador from San Salvador; Jody García from Guatemala City; and Joan Suazo from Tegucigalpa, Honduras.

A transition team for President Trump has asked scores of senior career diplomats to resign from their positions on Monday, as soon as Mr. Trump takes office, and many of those asked to step down intend to do so, two U.S. officials said.

The practice is common when a presidential transition occurs, but it is happening faster and on a larger scale than with previous administrations, one U.S. official said. That means a possible loss of valuable knowledge of both the American institution and global affairs at the start of the administration.

The Trump transition team at the State Department is led by aides to Marco Rubio, the Florida senator picked by Mr. Trump to replace Antony J. Blinken as secretary of state. Mr. Rubio is expected to be confirmed quickly by the Senate.

Some of the officials stepping down are at the level of assistant secretary or higher and run large bureaus in the department that focus on regions of the world or broad issues. Many of those positions were held by political appointees and will be vacated, which is expected during a transition. The Trump transition team asked for the resignations on Friday.

It is unclear what kinds of jobs the veteran diplomats, known as foreign service officers, will seek or get in the coming weeks or months. Career diplomats are members of a union that would try to protect them from being fired from the State Department if that were to happen unfairly.

Every president and their appointed secretary of state replaces all or most of the people in those senior positions early in an administration. In some cases, foreign service officers decide to retire, especially if they have served for more than two decades. In some cases, they have held top positions throughout the department already and have no clear advancement path when a new administration comes in.

Among the top department officials who had earlier planned to step down is Daniel J. Kritenbrink, a longtime diplomat who has served as assistant secretary of East Asian and Pacific affairs in the Biden administration and is a former ambassador to Vietnam. He retired last Friday after 31 years in the State Department.

Ambassadors also offer their resignations, which the incoming president and secretary of state accept in most cases.

Ambassadors have been announcing their departures. Jeffrey Prescott, a political appointee representing the United States at United Nations agencies in Rome, posted on social media about his departure on Monday and his work on U.N. food programs during his tenure.

Like top officials at the State Department in Washington, ambassadors are a mix of political appointees and career diplomats. Many of the political appointees are wealthy donors to the president’s campaign, whether a Democratic or Republican one, and have little experience in diplomacy or global affairs.

At a confirmation hearing for Mr. Rubio last week, Senator Tim Kaine, Democrat of Virginia, asked him to leave career diplomats serving as ambassadors in place until new ones appointed by Mr. Trump are confirmed and in place to do their jobs.

On Jan. 13, R. Nicholas Burns, the ambassador to China, said in an email that he was departing Beijing for Washington and then would leave the State Department. Mr. Burns had an unusual career: He was a foreign service officer for many decades and eventually became the third-ranking official at the department. He left for other jobs, including a teaching post at the Harvard Kennedy School, and then returned to serve as an ambassador under President Biden.

Mr. Burns said he was proud to have represented the United States during an “enormously difficult and challenging time” in U.S.-China relations.

And he defended the federal government and its many employees, saying that “we have truly outstanding men and women in public service” and that “they are working very hard and often at great personal sacrifice to represent us in seriously challenging circumstances in China and around the world.”

“I believe they deserve our full support going forward,” he added.

Gazans took in the scale of devastation to their old neighborhoods and Israelis awaited news about three newly released hostages as a day-old cease-fire between Hamas and Israel continued to hold on Monday.

With the 15-month war paused, Palestinians have been returning to parts of the Gaza Strip they had fled, picking their way through vast swaths of rubble and trying to salvage what they could — a sofa, a mattress, a chair or a crate — from the wreckage of their former homes.

“People can barely recognize the crushed places where they used to live,” said Montaser Bahja, an English teacher, a day after visiting his old neighborhood in the northern city of Jabaliya.

In a video shared with The New York Times, Mr. Bahja, 50, can be seen hurrying through the streets with his son Alhassan, 21, and trying to reconcile the piles of rubble that loom on either side with their memories.

“This is Fahmy Abu Warda’s home; this is Abu Shaaban’s home,” Alhassan is heard saying.

In Israel, which celebrated the return of the first group of hostages released by Hamas as part of the truce, the authorities offered only the broadest of descriptions of their conditions. The Israeli health ministry and Sheba Medical Center, where the three women are staying in a closed wing with family members, said their primary commitment was to safeguard the former captives’ privacy as they received medical and psychological care.

“I’m happy to report that they are in stable condition,” said one of their doctors, Prof. Itai Pessach. “That allows us, and them, to focus on what is the most important thing for now: uniting with their families.”

But Israelis did hear from one of the women on Monday.

“I have returned to life,” Emily Damari, 28, said on social media, describing herself as “the happiest person in the world.”

Ms. Damari was one of about 250 people taken hostage in the Hamas-led attack of Oct. 7, 2023. About a hundred are believed to still be in Gaza, and about a third of those are believed to be dead. The militants also killed some 1,200 people that day, Israel says.

Under the terms of the cease-fire, Hamas agreed to free 33 hostages in exchange for the release of more than 1,000 Palestinians from Israel’s prisons. The return of the three hostages was followed by the release of 90 prisoners, and the exchanges are to take place once a week during the 42-day truce.

Palestinians in the Gaza have rejoiced at the pause in fighting. Gazan health officials say more than 47,000 people have been killed during the Israel assault that began after the 2023 Hamas attack; they do not distinguish between civilians and fighters.

But the scenes playing out in the enclave and in Israel on Monday embodied the bittersweet emotions felt on both sides of the border.

As the truce came into effect on Sunday, celebrations replaced explosions, and hundreds of trucks with aid began rolling into Gaza, where residents have endured a harsh year of hunger and deprivation. In Israel, the returned hostages were met with jubilant embraces from relatives and friends. And fireworks and cheering crowds greeted the newly freed Palestinian prisoners in the Israeli-occupied West Bank.

But joy was shadowed by uncertainty. The next round of negotiations between Hamas and Israel are expected to be even more difficult than the ones that led to the 42-day cease-fire.

The fate of more than 60 other hostages and thousands of other Palestinian prisoners in Israel, to say nothing of the prospect of a long-term end to the fighting, depends on the extension of the deal.

“This is a moment of tremendous hope — fragile, yet vital,” Tom Fletcher, the United Nations undersecretary general for humanitarian affairs, said on social media.

The rejoicing has also been dimmed by the expectations of prolonged hardship to come and the knowledge that there is as yet no comprehensive plan for how Gaza will be rebuilt. Many of the two million residents there have been displaced at least once,

The task ahead is unimaginably daunting.

Gazans returning to the southern city of Rafah found it mostly flattened. The mayor said that 60 percent of homes had been destroyed, as well as 70 percent of the city’s sewage system.

But after 15 months of hunger and scarcity, food and other vital supplies are now surging into Gaza. More than 630 trucks entered the enclave on the first day of the cease-fire, according to United Nations officials.

During the fighting, far fewer made it in — and when they did, it was often too dangerous to get aid to where it was needed. Israel’s military campaign beat Hamas back without replacing it, creating a power vacuum. As the enclave descended into lawlessness, desperate crowds and organized gangs swarmed the trucks in hopes of securing a package of food or a bag of flour.

The scenes were not repeated on Sunday and Monday.

“What was very noticeable is that none of the trucks that entered yesterday were looted,” said Nebal Farsakh, a spokeswoman for the Palestinian Red Crescent, a humanitarian aid organization.

But violence did break out in the West Bank, where Israeli settlers set upon Palestinian villages amid anger over the planned release of Palestinian prisoners, some of whom were convicted of deadly attacks against Israelis, in the cease-fire deal.

In Sinjil, a village south of Nablus, dozens of men, some carrying slingshots, threw stones and set houses on fire, according to residents and videos verified by The Times.

“People screamed as their homes were burning,” said one resident, Ayed Jafry, 45. Several people were injured, including an 86-year-old man, he said.

In the aftermath of the Hamas attack that set off the war in Gaza, Israeli leaders vowed to wipe out the militants once and for all. But in the first two days of the cease-fire, Hamas has been making clear that it intends to remains a major force in the territory.

In an interview with The Times, a Hamas official, Mousa Abu Marzouk, suggested that at least some senior members of the group hoped to engage in “dialogue” with the United States, even though the American government has designated it as a terrorist organization since 1997.

Mr. Abu Marzouk, who is based in Qatar, said Hamas was ready to welcome an envoy from the Trump administration despite a longstanding American policy to provide Israel with weapons and defend it at international institutions.

“He can come and see the people and try to understand their feelings and wishes,” he said of the envoy, “so that the American position can be based on the interests of all the parties, and not only one party.”

Reporting was contributed by Hiba Yazbek, Natan Odenheimer, Fatima AbdulKarim, andAfif Amireh.

The White House on Monday said that President Trump would withdraw the United States from the Paris Agreement, the pact among almost all nations to fight climate change.

By withdrawing, the United States would join Iran, Libya and Yemen as the only four countries not party to the agreement, under which nations work together to keep global warming below levels that could lead to to environmental catastrophe.

The move, one of several energy-related announcements in the hours immediately following his inauguration, is yet another about-face in United States participation in global climate negotiations. During his first term Mr. Trump withdrew from the Paris accord, but then President Biden quickly rejoined in 2020 after winning the White House.

Scientists, activists and Democratic officials assailed the move as one that would deepen the climate crisis and backfire on American workers. Coupled with Mr. Trump’s other energy measures on Monday, withdrawal from the pact signals his administration’s determination to double down on fossil-fuel extraction and production, and to move away from clean-energy technologies like electric vehicles and power-generating wind turbines.

“If they want to be tough on China, don’t punish U.S. automakers and hard-working Americans by handing our clean-car keys to the Chinese,” said Gina McCarthy, former White House climate adviser and former head of the Environmental Protection Administration. “The United States must continue to show leadership on the international stage if we want to have any say in how trillions of dollars in financial investments, policies and decisions are made.”

To pull the United States out of the Paris Agreement, the Trump administration will need to formally submit a withdrawal letter to the United Nations, which administers the pact. The withdrawal would become official one year after the submission. It was not immediately clear whether the administration had already submitted the formal withdrawal letter.

U.S. efforts to reduce greenhouse gas emissions were already stalling in 2024, and Mr. Trump’s entry into office makes it increasingly unlikely the United States will live up to its ambitious pledges to cut them even further. Emissions dropped just a fraction last year, 0.2 percent, compared with the year earlier, according to estimates published this month by the Rhodium Group, a research firm.

Despite continued rapid growth in solar and wind power that was spurred by the previous administration’s signature climate legislation, the Inflation Reduction Act, emissions levels stayed relatively flat last year because demand for electricity surged nationwide, which led to a spike in the amount of natural gas burned by power plants.

The fact that emissions didn’t decline much means the United States is even further off-track from hitting Mr. Biden’s goal, announced last month under the auspices of the Paris Agreement, of slashing greenhouse gases 61 percent below 2005 levels by 2030. Scientists say all major economies would have to cut their emissions deeply this decade to keep global warming at relatively low levels.

In a scenario where Mr. Trump rolled back most of Mr. Biden’s climate policies, U.S. emissions might fall only 24 to 40 percent below 2005 levels by 2030, the Rhodium Group found.

“President Trump is choosing to begin his term pandering to the fossil fuel industry and its allies,” the Union of Concerned Scientists said in a statement. “His disgraceful and destructive decision is an ominous harbinger of what people in the United States should expect from him and his anti-science cabinet.”

Since 2005, United States emissions have fallen roughly 20 percent, a significant drop at a time when the economy has also expanded. But to meet its climate goals, U.S. emissions would need to decline nearly 10 times as fast each year as they’ve fallen over the past decade.

The United States is also a major exporter of emissions. Because of policies promoted by both Republicans and Democrats, the United States is now producing more crude oil and natural gas than any nation in history. Mr. Trump has vowed to further ramp up production and exports.

While the United States may not be party to the Paris Agreement, it will still be part of the U.N. Framework Convention on Climate Change, which hosts annual climate negotiations known as COPs. This year’s COP will be held in Brazil in November and nations will be announcing new pledges for emissions reductions.

One recent study by Climate Action Tracker, a research group, found that, if every country followed through on the pledges they have formally submitted so far, global average temperatures would be on track to rise roughly 2.6 degrees Celsius, or 4.7 degrees Fahrenheit, above preindustrial levels by the end of the century, well above the 1.5 degrees Celsius the Paris Agreement originally set as a goal.

“Trump’s irresponsibility is no surprise,” said Christiana Figueres, a Costa Rican diplomat and an architect of the Paris Agreement in 2015. “In time, Trump will not be around but history will point to him and his fossil fuel friends with no pardon.”