WASHINGTON — President Donald Trump moved aggressively to tighten the nation’s immigration controls Wednesday, signing executive actions to jump-start construction of his promised U.S.-Mexico border wall and cut federal grants for immigrant-protecting “sanctuary cities.” He also weighed a plan to pause the flow of refugees to the United States and indefinitely bar all those fleeing war-torn Syria.

“Beginning today the United States of America gets back control of its borders,” Trump declared during a visit to the Department of Homeland Security. “We are going to save lives on both sides of the border.”

The actions, less than a week into Trump’s presidency, fulfilled pledges that animated his candidacy and represented a dramatic redirection of U.S. immigration policy. They were cheered by Republican allies in Congress, condemned by immigration advocates and were the trigger for new tension with the Mexican government.

Trump is expected to wield his executive power again later this week with the directive to dam the refugee flow into the United States for at least four months, in addition to the open-ended pause on Syrian arrivals.

The president’s upcoming order is also expected to suspend issuing visas for people from several predominantly Muslim countries — Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen — for at least 30 days, according to a draft executive order obtained by The Associated Press.

Trump is unveiling his immigration plans at a time when detentions at the nation’s southern border are down significantly from levels seen in the late 1990s and early 2000s. The arrest tally last year was the fifth-lowest since 1972.

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Deportations of people living in the United States illegally also increased under President Barack Obama, though Republicans criticized him for setting prosecution guidelines that spared some groups from the threat of deportation, including those brought to the United States illegally as children.

As a candidate, Trump tapped into the immigration concerns of some Americans who worry both about a loss of economic opportunities and the threat of criminals and terrorists entering the country. His call for a border wall was among his most popular proposals with supporters.

Immigration advocates and others assailed the new president’s actions. Omar Jadwat, director of the American Civil Liberties Union’s Immigrants’ Rights Project, said the president’s desire to construct a border wall was “driven by racial and ethnic bias that disgraces America’s proud tradition of protecting vulnerable migrants.”

Advocates who work with immigrants and refugees on Long Island complained about what they see as the criminalization of immigrants, an erosion of protections for vulnerable groups and the threat to families that could be broken up by deportations.

Walter Barrientos, Long Island organizer in Brentwood for Make the Road New York, a Latino-advocacy group, said the order “demonstrates what Trump promised, which is creating a mass deportation and criminalization of immigrants and refugees, and not affording them the civil rights and protections that everyone in this country is entitled to.”

New York City Mayor Bill de Blasio called the order “very vague. . . . If anything actually starts to move, the city of New York will take legal action to stop the executive order from hurting our people and our city.”

How Trump plans to pay for the wall project is murky. While he has repeatedly promised that Mexico will foot the bill, U.S. taxpayers are expected to cover the initial costs and the new administration has said nothing about how it might compel Mexico to reimburse the money.

In an interview with ABC News earlier Wednesday, Trump said, “There will be a payment; it will be in a form, perhaps a complicated form.”

In a nationally televised speech late Wednesday, Mexican President Enrique Pena Nieto condemned the U.S. decision. “I regret and reject the decision of the U.S. to build the wall,” he said. “I have said time and again, Mexico will not pay for any wall.”

Pena Nieto did not directly mention whether he still would make a scheduled visit to the White House on Jan. 31, but he said he would await reports from high-level Mexican officials meeting with Trump administration officials in Washington.

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Congressional aides say there is about $100 million of unspent appropriations in the Department of Homeland Security account for border security, fencing and infrastructure. That would allow planning efforts to get started, but far more money would have to be appropriated for construction.

Trump has insisted many times the border structure will be a wall. The order he signed referred to “a contiguous, physical wall or other similarly secure, contiguous and impassable physical barrier.”

With Víctor Manuel Ramos and Matthew Chayes