Imagine Andres Obrador, who’s set to be sworn in as Mexico’s new president next Saturday, waking up yesterday and having this story shoved in front of him by an anxious aide.

What will we be offering our friends down south in exchange for them agreeing to host asylum applicants, assuming they’re willing to do so at all? Maybe we can let them off the hook for paying for the wall, which doesn’t exist and which they were never going to pay for in the first place.

The new plan is clever, though, in purporting to reframe the basic question of asylum cases, namely, does the applicant reasonably fear persecution in his or her home country? So long as they’re camped out in Mexico, Team Trump will argue, whether they fear persecution back home is irrelevant. The relevant question is whether they fear persecution in Mexico. If the answer’s no, well, then, they can wait in Mexico.

Central Americans who arrive at U.S. border crossings seeking asylum in the United States will have to wait in Mexico while their claims are processed under sweeping new measures the Trump administration is preparing to implement, according to internal planning documents and three Department of Homeland Security officials familiar with the initiative.

According to DHS memos obtained by The Washington Post on Wednesday, Central American asylum seekers who cannot establish a “reasonable fear” of persecution in Mexico will not be allowed to enter the United States and would be turned around at the border.

The plan, called “Remain in Mexico,” amounts to a major break with current screening procedures, which generally allow those who establish a fear of return to their home countries to avoid immediate deportation and remain in the United States until they can get a hearing with an immigration judge. Trump despises this system, which he calls “catch and release,” and has vowed to end it.

According to a Mexican official who spoke to WaPo, their law doesn’t allow people applying for asylum in another country to remain in Mexico. And processing mass requests for asylum in Mexico would be logistically difficult since the Mexican government has far fewer asylum officers than the U.S. does. The new president is also unlikely to be accommodating, as the last thing he’d want to do after being sworn in is to show his country that Trump can push him around. In fact, Obrador complained during the campaign that he was tired of Mexico doing America’s “dirty work” in catching immigrants before they crossed over into the U.S. He wants Washington to pony up more aid money to Central American countries (and southern Mexico), to help address the conditions that are supposedly driving people north to America.

Hostility from the incoming administration is one problem. Another problem is that the Central Americans in the caravan actually might soon face a reasonable fear of persecution in Mexico, assuming they don’t already.

The mayor of Tijuana has declared a humanitarian crisis in his border city and says that he has asked the United Nations for aid to deal with the approximately 5,000 Central American migrants who have arrived in the city.

Mayor Juan Manuel Gastelum says that the Mexican federal government has provided little assistance and he is not going to commit the city’s public resources to dealing with the situation.

Gastelum said on Grupo Formula radio Friday that Tijuana does not have the necessary infrastructure to adequately attend to the migrants.

Some Tijuanans have complained of an “invasion” from the south. Now Trump wants Obrador to tell them that the visitors might be there for months while they’re waiting to hear from the U.S. on asylum.

There’s another hiccup, per Politico. Here’s the relevant U.S. statute on asylum:

(i) Conduct by asylum officers.-An asylum officer shall conduct interviews of aliens referred under subparagraph (A)(ii), either at a port of entry or at such other place designated by the Attorney General.

(ii) Referral of certain aliens.-If the officer determines at the time of the interview that an alien has a credible fear of persecution (within the meaning of clause (v)), the alien shall be detained for further consideration of the application for asylum.

Typically when the word “shall” appears in federal law it means there’s no executive discretion in the matter. Trump’s proposing that asylum applicants not be detained after their initial interview but rather turned around and sent to Mexico to wait while their application is processed. The statute doesn’t seem to allow that. He’ll be sued lickety split once the new policy is in place, which it isn’t yet.

Back to the key question, though. What’s Trump’s leverage in getting Obrador to agree to this? I noticed this piece at Forbes earlier today pointing out that there’s just one week left in the 60-day review period for the new trade agreement between the U.S., Canada, and Mexico. The formal signing was supposed to happen next Friday at the G20. Is Trump thinking that he’ll hold U.S. support for the deal hostage unless and until Obrador agrees to host asylum applicants? That might be tricky, as Obrador may relish the opportunity to have his new administration renegotiate the deal. The standoff over asylum might end up as a dealbreaker for the trade agreement on both sides.