Donald Trump stood on the South Lawn of the White House on June 11, waving a folded piece of paper in front of the cameras that he said was an agreement with Mexico to address the migrant crisis at the border. “That’s the agreement that everybody says I don’t have,” he proclaimed. “I’m going to let Mexico do the announcement at the right time.”

A photograph of the agreement revealed that it had set a deadline of 45 days for the U.S. to determine if Mexico had “not sufficiently achieved results in addressing the flow of migrants to the southern border of the United States.”

But with the deadline approaching on Monday, U.S. detention centers continue to be overwhelmed by the flow of asylum seekers from Guatemala, El Salvador and Honduras. It’s unclear whether Mexico will make any more changes to its handling of Central Americans seeking asylum, or whether the Trump Administration will punish it if it fails to do so.

This weekend, Secretary of State Mike Pompeo will travel to Mexico City to try to firm up a deal with Mexico. But experts say that there are a number of major obstacles to any agreement that would have a significant effect on the migrant crisis.

Pompeo’s task got even harder in mid-July when a related deal with Guatemala appeared to have fallen apart. The Trump Administration had hoped to get the Central American country to sign to what is called a “safe third country” agreement, which would require them to assume responsibility for asylum seekers from El Salvador and Honduras. But after Guatemala’s equivalent to the Supreme Court denied the president the authority to sign such a deal, he canceled a trip to Washington.

“If Mexico sees Guatemala is no longer being a player in this regional asylum burden sharing agreement, Mexico might be much more hesitant to jump in,” Sarah Pierce, a policy analyst at the Migration Policy Institute, told TIME.

The argument for “safe third country” is that people seeking asylum would not travel through multiple countries to get to the United States, instead stopping in the first safe place they can find. In theory, if it were implemented with multiple countries, it would punt asylum claims down the North American continent and stem the migrant crisis at the U.S.-Mexico border. But critics note that few of the countries the asylum seekers are traveling through are very safe.

“I wouldn’t call it a safe third country agreement, because Mexico is not a safe country,” said Guadalupe Correa-Cabrera, who recently led a State Department-funded study of organized crime and trafficking in persons in Central America and along Mexico’s eastern migration routes.

Read More: President Trump Wants Asylum Seekers to Stay in Mexico. Here’s How That Would Work

In mid-July, the international humanitarian group Doctors Without Borders noted that the U.S. was deporting asylum seekers to an area in Mexico classified by the U.S. State Department with the highest travel advisory: “Level 4: Do not travel.” The same category also includes North Korea, Sudan, South Sudan, Venezuela, Syria, Somalia, Libya, Iran and Afghanistan.

Anita Isaacs, a fellow at the Wilson Center who has consulted on corruption and organized crime in Central America for the State Department, said there’s a similar problem with Guatemala.

“It’s clear that Guatemala is not a safe country for Guatemala, let alone for anyone else,” she told TIME.

Last week, the Trump Administration announced a new unilateral change to U.S. asylum policy, appearing to jump the gun on the 45-day deadline.

The new rule bars Guatemalan migrants who pass through Mexico — as the vast majority do — from applying for asylum in the United States unless their claims had already been rejected in Mexico, with a few limited exceptions, including one for victims of human trafficking.

The rule would also bar migrants from El Salvador or Honduras from applying for asylum unless their claims were first rejected in Guatemala or Mexico.

But it is unclear whether the rule can be implemented. The policy, which rests on shaky legal ground, is already facing a lawsuit from the ACLU. So far, it does not appear to have affected border enforcement. And the deportation of these now-ineligible asylum seekers may not be feasible without cooperation from other countries.

“Asylum seekers subject to the new rule would be placed in either expedited or regular removal proceedings, both of which lead to deportation to the home country,” Sarah Pierce, a policy analyst at the Migration Policy Institute, told TIME.

“Especially when you’re talking about the Central American countries, there is paperwork that needs to be exchanged between the U.S. government and those countries before deportation can be executed,” Pierce said.

Contact us at letters@time.com.