Mexico has not accepted that the United States send it an unlimited number of asylum seekers, Foreign Minister Marcelo Ebrard said, before meetings with US officials on Friday to determine the expansion of a controversial programme.
Under pressure from US President Donald Trump, Mexico agreed last week to expand the programme, which forces mostly Central American asylum seekers to return to Mexico to await the outcome of their US asylum claims.
Ebrard said officials would discuss which cities the programme, known as Remain in Mexico, would expand to, as well as how to measure the number of people and which nationalities Mexico would accept.
"Today, there is a meeting with US authorities, to learn, to discuss the ports of entry and how the number will be measured, because Mexico has not accepted that it be undetermined," he said in a news conference.
Currently, the programme operates in Tijuana, Mexicali and Ciudad Juarez. Close to 12,000 people have been returned to Mexico since January.
'Safe third country'
Mexico has also agreed to consider a plan that could make it a "safe third country" in which asylum seekers would have to seek refuge instead of in the US, if Mexico does not bring down immigration flows by mid-July through enforcement measures, officials have said.
Trump confirmed on Friday said that the deal struck in return for not imposing threatened tariffs on Mexico included a plan to establish a "safe third country" agreement.
Asked in a Fox News interview if the plan included that option if Mexico cannot stem the flow of Central American migrants headed for the US, Trump said, "It's exactly right, and that's what's going to happen."
Mexican officials have previously said, however, that Mexico would begin talks about a possible "safe third country" agreement if migration at Mexico's southern border did not decrease within the 45 days.
"We would start conversations about what they would like, which is for Mexico to become a safe third country," Ebrard told a Mexican radio programme earlier this month.
Immigration rights groups have slammed to possible "safe third country" agreement, saying that it would endanger asylum seekers by requiring them to make their claims in a country experiencing high levels of violence.
Meanwhile on Friday, Trump also named Tom Homan as "Border Czar".
Homan is a veteran of the US Immigration and Customs Enforcement and served as the agency's acting head during the first year of Trump's presidency. He retired last year, after increasing arrests of non-criminal immigrants.