Central Americans seeking asylum in the United States could soon spend months or even years in Mexico waiting for their cases to be heard, but they will not yet be required to seek asylum there first.

President Donald Trump has pushed for a so-called “safe third country” agreement in which people fleeing violence and poor economic conditions would be required to seek asylum in the first country they reach.

If Mexico agreed, the policy would dramatically reduce the thousands of immigrants from Guatemala, Honduras and El Salvador seeking asylum at the U.S. border each month.

But after a weeklong standoff with the Mexican government, Trump backed down from threatened tariffs, saying that he has reached an agreement to deal with the migrant crisis. For now, neither side has announced that the deal includes a “safe third country” provision.

Officials agreed to expand the “Remain in Mexico” program, in which migrants seeking asylum in the United States wait in Mexico while their claims are adjudicated. Mexico will also send 6,000 National Guard troops to its border with Guatemala to keep migrants out.

After the New York Times reported that the major provisions had already been agreed to months ago, Trump tweeted that more is coming.

“Some things not mentioned in yesterday press release, one in particular, were agreed upon,” he tweeted. “That will be announced at the appropriate time.”

But Mexico’s foreign minister said on Monday that there is no secret deal, contrary to what Trump tweeted.

However, if the currently agreed-upon measures do not significantly reduce the number of migrants at the U.S. border, Mexico might be willing to consider a mulitlateral overhaul of regional asylum rules with other countries, including Panama and Brazil, as an alternative to a safe third country agreement.

Here’s what you need to know about the dispute.

How does asylum work now?

Currently, migrants seeking asylum at the U.S. border may be diverted to detention centers, makeshift shelters or tent cities while they wait for their claim to be processed. If there is no space, migrants may be released into the United States — an option that the president has previously derided as “catch and release” — where they often seek help from nearby charities whose resources are strained under the influx of people.

But with a surge in asylum seekers from Central America reaching the U.S. border, Trump has pushed Mexico to adopt new policies.

What is the ‘Remain in Mexico’ program?

In January, the Department of Homeland Security began a pilot program in which people applying for asylum in the United States would wait in Mexico while their cases were being heard.

Due to immigration court backlogs,those migrants “are looking at waiting in Mexico for years, right now,” says Sarah Pierce, a policy analyst at the Migration Policy Institute.

Experts caution that Mexico is not necessarily able to provide safety to asylum seekers.

“There’s a lot of violence has sort of been on an upward trend and increasing [in] Mexico, homicides, other violent crime,” says Leah Chavla, a policy adviser at the Women’s Refugee Commission. “There’s corruption migrants already face, really high levels of exploitation at the hands of both state actors and non state actors.”

How does ‘safe third country’ work?

The concept of a safe third country originated in the early 1990s. In response to an increase in the number of asylum applications, the European Union developed a definition of a safe third country, “a non-EU country through which the asylum seeker has transited and to which h/she may be returned” without fear of persecution.

The U.S. and Canada already have a “safe third country” asylum agreement, which has been in effect since 2004.

The two countries “were seeing increases in asylum seekers, especially right before the year 2000,” explains Pierce. “And a disproportionate number of those claims were being made in Canada. Migrants were transiting through the United States to get to Canada to apply for asylum.”

Supporters of tighter immigration rules favor “safe third country” over Remain in Mexico.

The Remain in Mexico program “is like a low calorie version of a safe third country agreement,” says Mark Krikorian, executive director of the Center for Immigration Studies, which advocates for lower immigration rates and has previously expressed support for a safe third country policy between the U.S. and Mexico.

What else could Mexico do?

Experts said the same goals could also be achieved through some other equivalent program, such as a regional agreement.

“It’s hard to say [what the last term of the agreement is], because both the U.S. government and the Mexican government have been very vague about the sort of secondary agreement that happened,” says Pierce. “But it sounds as if it would be a regional asylum overhaul, that would be similar to us just having a safe third country agreement with Mexico. It sounds like it would kind of go down the line. And it would include Guatemala, and possibly also Panama and Brazil, so that the burden of asylum seekers would then be shared across these four to five countries.”

Still, experts warn that some of those countries may not be able to protect asylum seekers from the dangers they are fleeing.

“Would asylum seekers actually be safe in these countries?” says Pierce. “If they’re fleeing gang violence, for example, would gang members still have access to them in Guatemala? Or in Mexico? And I think that’s very much an open question.”

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