Biden is expected to sign an order allowing him to seal the border with Mexico

President Biden is expected to sign an executive order on Tuesday allowing him to temporarily close the U.S. border with Mexico to migrants in the event of a large influx of migrants, overturning longstanding protections for asylum seekers in the United States.

Several people familiar with the plans say senior Biden aides have told members of Congress in recent days that he will sign the order at the White House along with South Texas mayors.

“I have been informed of the impending executive order,” said Democratic Representative Henry Cuellar of Texas, who had previously called on the president to strengthen border controls. “I certainly support it, as I have been advocating these measures for years. Although the order has not yet been released, I support the details that have been provided to me so far.”

The order is the most restrictive border policy ever implemented by Biden or any other modern Democrat, and is reminiscent of President Donald J. Trump’s 2018 efforts to curb migration, which were attacked by Democrats and blocked by federal courts.

Although the executive action is almost certain to face legal challenges, Biden is under enormous political pressure to address illegal immigration, one of voters’ top concerns ahead of the November presidential election.

The decision highlights how immigration policy has shifted sharply to the right over the course of Biden’s presidency, with polls suggesting that support for border measures that Democrats once condemned and that Trump championed is growing even within the president’s party.

The order would allow border officials to deter migrants from seeking asylum and quickly expel them once the number of crossings exceeds a certain threshold. (Minors crossing the border alone are likely exempt from the restrictions, according to an official briefed on the order.)

Asylum seekers are normally released to the United States to await court dates where they can argue their cases in court, but a huge backlog means it can take years for those cases to go to trial.

Administration officials debated whether Biden should allow the border to be closed this year if an average of more than 5,000 migrants per day attempted to cross the border illegally during a week or more than 8,500 migrants attempted to cross the border illegally on any given day.

In recent days, White House officials have discussed a cap of 2,500 illegal border crossings per day. That would mean the border could be closed to asylum seekers once Biden signs the executive order, as the daily total currently exceeds that number.

However, people involved in the negotiations said the details were still being worked out.

The number of people crossing the border illegally has dropped significantly in recent months after reaching a record high in December, when about 10,000 people made their way to the United States each day.

Biden administration officials, panicking over the numbers in December, urged Mexico to do more to curb migration. Since then, Mexican officials have used charter flights and buses to move migrants further south and away from the United States.

On Sunday, border officials arrested more than 3,500 people crossing the border without authorization, consistent with the trend in recent weeks, according to a person familiar with the data.

The executive action will likely mirror a measure in a failed bipartisan bill this year that proposed some of the most sweeping restrictions on border security that Congress had considered in years. The bill would have provided billions in funding for the border, including hiring thousands of asylum officers to process the claims.

But Republicans killed the bill in February, arguing it was not strong enough. Many of them, egged on by Trump, did not want to concede a victory to Biden in the House in an election year. The president’s advisers hope the executive order will give him an opportunity to criticize Republicans for their decision to kill the bipartisan bill that would provide billions of dollars to the Department of Homeland Security.

“Even though Republicans in Congress have decided to stand in the way of additional border security, President Biden will not stop fighting to ensure border and immigration officials have the resources they need to secure our border,” Angelo Fernández, a White House spokesman, said in a statement on Monday. He did not confirm the plans but said the administration is “reviewing a range of policy options, and we remain committed to taking action to fix our broken immigration system.”

Government officials have said they would not favor executive action and that they expect any order would have to be challenged in court.

“What we need is legislation,” Homeland Security Secretary Alejandro N. Mayorkas said last month.

“Executive measures will be challenged,” he added. “I am convinced of that. And then the question will be: what is the outcome of these proceedings? Laws are a safer solution.”

The American Civil Liberties Union led the charge against the Trump administration’s attempt to block asylum in 2018, which resulted in the policy being halted by federal courts. The group has signaled that it is prepared to challenge any order restricting asylum at the border.

“We must re-examine the EO before deciding whether to sue, but any action that effectively strips protections from desperate migrants would raise serious legal problems, as was the case when the Trump administration tried to eliminate the right of asylum,” said Lee Gelernt, an ACLU attorney who led the lawsuit against many of Trump’s actions.

While Republicans have long attacked Democrats on border security, Biden has faced calls for stronger border enforcement from members of his own party in recent years.

Democratic Rep. Tom Suozzi of New York, who won a special election to the House this year in part by calling for tougher immigration measures, sent a letter to Biden last month urging him to issue an executive order that would restrict asylum rights.

“I think this is very, very important, not just for Democrats or for political reasons, but it’s important for America,” Suozzi said in an interview. “This is something that people are very concerned about.”

But passing the order also carries political risks. Republicans have questioned in recent days why Biden did not take unilateral action at the border sooner. In January, he told reporters that he had done “everything I can do” at the border and now needed help from Congress.

“The American people know better,” spokesman Mike Johnson, Republican of Louisiana, wrote in a social media post on Monday.

As a sign of how much politics have changed on this issue, Biden, as the candidate in 2019, sharply criticized Trump’s policies in a debate.

“This is the first president in the history of the United States of America to force anyone seeking asylum to do so in another country,” Biden said at the time. “This has never happened before.”

“You come to the United States and present your case,” he added, “and so you apply for asylum based on the following premise: Why I deserve it under American law.”