The port of entry that connects Tijuana to San Diego, the country's busiest border crossing, will allow only 20 migrants to claim asylum a day beginning Friday, a Mexican government official said Friday. Prior to the policy change, Customs and Border Patrol officers had processed up to 100 individuals a day.

The capacity reduction — known in immigration circles as "metering" — came the same day that the Trump administration implemented its "Migrant Protection Protocol," a sweeping policy change that forces asylum seekers to stay in Mexico while they await their U.S. immigration court hearings. Prior to the policy change, asylum seekers waited in the United States, either behind bars or non-detained but monitored.

U.S. government officials have told Mexican officials that they would be processing and transferring back 20 immigrants per day beginning January 25 at the San Ysidro port of entry, a spokesperson for the Mexico Committee on Foreign Relations said during a press conference in Mexico City. They'll join the thousands of others who are waiting in Tijuana just to cross through the port of entry and claim asylum.

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"Accepting merely 20 people a day through the metering process at the San Ysidro port of entry is a sharp reduction from the past," said Ruby Powers, a Texas-based immigration attorney who volunteers in the border city. "It will continue to exacerbate an already intense backlog of asylum-seekers waiting in Mexico."

During the Mexico City press conference, the spokesperson for the Mexico Committee on Foreign Relations said while they didn't agree with the U.S.'s new protocol, they would comply. During meetings leading up to the policy announcement Thursday, U.S. government officials said that the protocol would be rolled out to the country's other ports of entry along the southern border, the Mexican government official said at the press conference.

Shelters in Tijuana are already at capacity, said Powers.

Now, with asylum seekers forced to wait in the border city instead of the U.S. and with a new, 6,000-something person caravan that arrived in December, there won't be enough resources to go around, said Katie Shepherd, an attorney with the Immigration Justice Campaign, in a telephone interview with CBS News.

"Availability of legal services, housing, and other basic necessities is extremely limited in Tijuana," Shepherd said. "This policy will lead to catastrophic results for vulnerable asylum-seeking families."

Metering, or only allowing a specific number of people to cross the border and claim asylum, has become common practice along the southern border and has immigration advocates concerned.

A class action lawsuit, Al Otro Lado, Inc. v. Nielsen, has challenged the Trump administration's practice of limiting the number of asylum seekers allowed to enter the country, claiming that U.S. government officials have "adopted a formal policy to restrict access to the asylum process at ports of entry by mandating that lower-level officials directly or constructively turn back asylum seekers at the border."

At one port of entry near Brownsville, Texas, Customs and Border Patrol officers didn't allow anyone to cross the border and claim asylum for four straight days earlier this month, said Jodi Goodwin, an immigration attorney based in Texas, in a telephone interview with CBS News.

The number of migrants waiting on the other side of the border grew to about 50 asylum seekers. Many were women and children, and forced to sleep on the streets, exposed to rain and wind, Goodwin said. Even though there's a shelter nearby, migrants fear that if they leave the immediate vicinity of the port of entry, they'll lose their place in line.

"The asylum seekers themselves are frustrated, they're bummed out, they've gone through so much to be able to make the journey to get here," Goodwin said "They expect that once they get there, they're going to be at least be processed, but that's just not the case."