The impact of the 2,500 figure means that the executive order could go into immediate effect, because daily figures are higher than that now.

The Democratic president is expected to unveil the actions — his most aggressive unilateral move yet to control the numbers at the border — at the White House on Tuesday at an event to which border mayors have been invited.

Five people familiar with the discussions on Monday confirmed the 2,500 figure, while two of the people confirmed the 1,500 number. The figures are daily averages over the course of a week. All the people insisted on anonymity to discuss an executive order that is not yet public.

While other border activity, such as trade, is expected to continue, the 1,500 threshold at which the border would reopen for asylum seekers could be hard to reach. The last time the daily average dipped to 1,500 encounters was in July 2020, at the height of the COVID-19 pandemic.

Senior White House officials, including chief of staff Jeff Zients and legislative affairs director Shuwanza Goff, have been informing lawmakers on Capitol Hill of details of the planned order ahead of the formal rollout Tuesday. But several questions remain about how the executive order would work, particularly how much cooperation the U.S. would need from Mexican officials to carry out the executive order.

The president has been deliberating for months over how to act on his own after bipartisan legislation to clamp down on asylum at the border collapsed because Republicans defected from the deal en masse at the urging of Donald Trump, the former president and presumptive Republican presidential nominee. Biden continued to consider executive action even though the number of illegal crossings at the southern border has declined for months, partly because of a stepped-up effort by Mexico.

Biden administration officials had waited until after Mexico’s presidential elections, held Sunday, to move on the U.S. president’s border actions. Mexico elected Claudia Sheinbaum, the nation’s first female leader, and Biden said in a statement Monday that he was committed to “advancing the values and interests of both our nations to the benefit of our peoples.” The two spoke on the phone Monday, although White House press secretary Karine Jean-Pierre declined to say whether they spoke about the pending order.

“We continue to look at all options on the table,” Jean-Pierre told reporters traveling with Biden on Air Force One on Monday evening.

The executive order will allow Biden to declare that he has pushed the boundaries of his own power after lawmakers, specifically congressional Republicans, killed off what would have been the toughest border and asylum restrictions in some time. Biden’s order is aimed at trying to head off any potential spike in border encounters that could happen later this year, closer to the November elections.

For Biden’s executive order, the White House is adopting some policies directly from the bipartisan Senate border deal, including the idea of limiting asylum requests once the encounters hit a certain number. The administration wants to encourage migrants to seek asylum at ports of entry by using the U.S. Customs and Border Protection’s CBP One app, which schedules about 1,450 appointments per day.

Administration lawyers have been planning to tap executive powers outlined in Section 212(f) of the Immigration and Nationality Act, which gives a president broad authority to block entry of certain immigrants into the U.S. if it is deemed “detrimental” to the national interest. It is the same legal rationale used by Trump to take some of his toughest actions on migration as president.

That has advocacy groups already preparing to challenge Biden’s immigration order in court.

“We will need to review the (executive order) before making final litigation decisions,” said Lee Gelernt, an attorney for the American Civil Liberties Union who led several of the most high-profile challenges to Trump’s border policies. “But a policy that effectively shuts down asylum would raise clear legal problems, just as (it) did when the Trump administration tried to end asylum.”

The White House is also sure to encounter vocal resistance from many Democratic lawmakers. California Sen. Alex Padilla, an outspoken critic of the Senate’s earlier border bill, said the pending executive order was “just not the solution we need and it’s very incomplete as a strategy.”

Padilla, who was also briefed by the White House on the proposal, wants an approach that works with countries throughout Latin America to address the poverty and unrest that drives migration to the United States. In recent weeks, Padilla has also pressed the White House for executive actions that benefit immigrants and said the message he has heard in return is, “We’re working on it.”

Biden will unveil his executive order flanked by several border mayors whom the White House invited for the announcement. Texas Mayors John Cowen of Brownsville and Ramiro Garza of Edinburg both confirmed their invitations, and San Diego Mayor Todd Gloria’s office also said the White House invited the mayor, but he could not attend due to scheduling difficulties.

Rep. Henry Cuellar, a Texas Democrat who said he was briefed on the plan, said he wishes the White House would have taken executive action a long time ago and said cooperation from Mexico would continue to be critical as the administration implements the order.

“If you think about the logistics, where else can they go?” Cuellar said. “If they’re not going to let them in, where do they go? Do they return them (to Mexico), or do they try to deport as many as they can? We did add a lot more money into ICE (U.S. Immigration and Customs Enforcement) so they can deport, but the easiest thing, of course, is just send them back to Mexico. You’ve got to have the help of Mexico to make this work.”

Jennifer Babaie, an attorney at Las Americas Immigrant Advocacy Center in El Paso, Texas, said she would be alarmed if Biden issued formal deportation orders without an opportunity to seek asylum. Advocates worry he may attempt that under the 212(f) provision.

Pandemic-era expulsion authority known as Title 42 had “a silver lining” for migrants because they could try again without fearing legal consequences, Babaie said. But a formal deportation order would expose them to felony prosecution if they attempted again and it would impose bars on legally entering the country in the future.

“This is even more extreme than (Title 42), while still putting people in harm’s way,” Babaie said.