Eusebio Gomez thought his arduous journey to the US and monthslong wait in the border town of Tijuana, Mexico, would end when he made it to American soil. But a shift in the Trump administration's immigration policy could mean more waiting.

The Mexican government said on Friday that the United States plans to return 20 migrants per day at the San Ysidro border crossing as they await an answer to their asylum requests. The practice could be one of the more significant changes to the immigration system in years.

Gomez, who was one of 25 names called for processing on Friday at San Ysidro, said he would feel far less safe waiting in Tijuana, with its sky-high homicide rate. The 18-year-old Honduran said he wanted to come to the US to escape violence.

"It's not about the dollar, it's about safety," Gomez said.

"The Mexican government doesn't agree with this unilateral move," but will accept the migrants under certain conditions, said Roberto Velasco, spokesman for Mexico's Foreign Relations Department. He said the US government wants to extend the practice, known as "remain in Mexico," to the rest of the border crossings.

Juan Portillo, 38, who arrived in Tijuana two months ago from Venezuela with his wife and seven-year-old daughter, said he was fleeing political oppression after protesting President Nicolas Maduro's government.

"We do not feel safe" in Tijuana, Portillo said, shortly before Mexican authorities whisked him, his family and seven others away in a van to be turned over to US authorities.

Advocacy groups condemned the idea. The Southern Poverty Law Center warned it would create more chaos at the border. Astrid Dominguez, director of the ACLU's Border Rights Center, said in a statement that it endangers lives. A legal challenge is expected.

Senator Dianne Feinstein of California and Jerrold Nadler of New York, both Democrats, released a statement warning that the changes would harm asylum seekers.

"Asylum seekers are easy prey for criminals and gangs in Mexico, but the Trump plan forces people to remain in harm's way, even if there is a significant possibility they will be persecuted or tortured in Mexico," they said in a statement.

Processing in Mexico

Velasco said around midday Friday that the first 20 migrants would be returned at the San Ysidro crossing, across from Tijuana, "in the next few hours."

He said all are Central Americans and all apparently had temporary visas in Mexico. That suggests they may have been part of last year's migrant caravans, many of whom had such visas. US officials have said Mexican asylum seekers and children travelling alone are exempt from the new policy.

Mexico will not accept migrants who have appealed a denial of asylum, unaccompanied children or people with health problems, Velasco said.

He did not say how or where Mexico would house the migrants, who might have to wait months or years for their asylum claims to be resolved.

Akbar Heybari of Iran, who has been paying for a Tijuana hotel with his wife and children, ages 15 and 12, said he would much prefer to stay with a niece who is studying medicine at the University of California, Irvine.

"It's good (in Tijuana), but we don't want to stay here more," said Heybari, a grape farmer who plans to seek asylum on grounds of government persecution for his political activities.

There are about 2,400 names on the asylum processing list at San Ysidro. US officials have been calling up to 100 names a day.

US authorities plan to bus asylum seekers back and forth to the border for court hearings in downtown San Diego, including an initial appearance within 45 days, according to a US official familiar with the plan who spoke on condition of anonymity because it was not yet publicly announced.

The Trump administration will make no arrangements for them to consult with attorneys, who may visit clients in Tijuana or speak with them by phone, the official said.

The US has witnessed a surge in asylum claims, especially from Central American families. Due largely to a court-imposed 20-day limit on detaining children, families are typically released with a notice to appear in immigration court. 

With a backlog of more than 800,000 cases, it can take years to settle cases.