MEXICO CITY (Reuters) – Mexico has not accepted that the United States send it an unlimited number of asylum seekers, Foreign Minister Marcelo Ebrard said, ahead of meetings with U.S. officials on Friday to determine the expansion of a controversial program.

Under pressure from U.S. President Donald Trump, Mexico agreed last week to expand the program, which forces mostly Central American asylum seekers to return to Mexico to await the outcome of their U.S. asylum claims.

Ebrard said officials would discuss which cities the program, known as Remain in Mexico, would expand to, as well as how to measure the number of people and which nationalities Mexico would accept.

Currently the program operates in Tijuana, Mexicali and Ciudad Juarez. Close to 12,000 people have been returned to Mexico since January.

In the deal reached a week ago, Mexico also agreed to a plan that could make it a “safe third country” in which asylum seekers would have to seek refuge instead of in the United States, if Mexico does not bring down immigration flows within 45 days through enforcement measures.

Trump on Friday confirmed that the deal struck in return for not imposing threatened tariffs on Mexico included a plan for safe third country.

Asked in a Fox News interview if the plan included the option if Mexico cannot stem the flow of Central American migrants headed for the United States, Trump said “It’s exactly right, and that’s what’s going to happen.”

(Reporting by Frank Jack Daniel in Mexico City and Makini Brice and Susan Heavey in Washington; Editing by Nick Zieminski and Susan Thomas)