WASHINGTON — The Trump administration is examining options for shutting entry points to the U.S. from Mexico in case the president follows through with his threat to close the border, a White House official said Wednesday.

Officials are discussing the possibility of closing select ports of entry, partly closing them, or shutting all entry points entirely, said the officials. The preparations are said to be somewhere between a theoretical discussion of options and implementation planning.

While President Donald Trump appeared to retreat from the threat on Tuesday, saying that Mexico had begun to crack down on migration to the U.S., his economic advisers are looking at ways to prevent large-scale disruptions of airline travel and trade should he follow through.

Mexico said it hasn’t changed its enforcement approach and Republican lawmakers have raised alarm about the economic consequences to the U.S. of cutting trade with its third-largest trading partner.

The peso declined on Wednesday to the lowest level of the day against the dollar.

Trump has made the threats amid a spike in crossings by undocumented immigrants in recent weeks. Trump has blamed Democrats for illegal crossings, saying Wednesday on Twitter that if the U.S. Congress fails to act, “Border, or large sections of Border, will close.” The president plans to highlight his policies on Friday, with a trip to the border city of Calexico, Calif.

Trump has struggled to make good on his signature 2016 campaign pledge to secure the southern border, and his policies have drawn criticism from Republicans and Democrats. Lawmakers have expressed dismay that undocumented children were separated from their parents and refused to give the president all the money he was seeking for a border wall, prompting Trump to declare a national emergency to obtain funds from elsewhere in the budget.

Discussions about closing the border are in motion despite comments from Trump on Tuesday suggesting he was pleased with steps the Mexican government had taken to address migration, prompting speculation the president was backing away from his border closure threat.

During a fundraising dinner on Tuesday night, Trump said Mexico was assisting the U.S. for the “first time in decades” and credited authorities there for “apprehending over a thousand people at the southern border” and returning them to their home countries. White House press secretary Sarah Huckabee Sanders also credited Mexico with offering asylum to additional migrants who might otherwise seek to enter the U.S.

But administration officials said Wednesday that Trump was still contemplating steps on the border, and looked to pressure Democrats.

“President Trump is encouraged by the new cooperation we’ve seen from Mexico, which at this point has been more helpful at addressing this emergency than congressional Democrats,” White House spokesman Hogan Gidley said Wednesday. “But this dangerous crisis has to be ultimately addressed by Congress, and if it’s not, the president has been clear that all options remain on the table to secure the border and protect the American people.”

The number of migrants Mexico has returned to their home countries in January and February hasn’t changed much since last year.

The White House is seeking Democratic support to changes to current immigration laws that would allow federal agents to more easily detain and deport those who have entered the country without documentation. But Trump was unable to win similar concessions during a 35-day government shutdown earlier this year, and fellow Republicans have shown little appetite for a border closure that could damage the economy.

“Closing down the border would have a potentially catastrophic impact” on the economy, and “I would hope he wouldn’t be doing that,” Senate Majority Leader Mitch McConnell, a Kentucky Republican, said Monday.

The U.S. Chamber of Commerce warned Monday that the president’s threats create “a degree of economic uncertainty that risks compromising the very gains in growth and productivity that policies of the Trump Administration have helped achieve.”