As early as Friday, U.S. immigration officials will begin to implement the so-called "Remain in Mexico" policy, the Department of Homeland Security said Thursday. The plan, first announced in December, would force asylum seekers to wait in Mexico while their immigration claims are processed — an idea that immediately drew criticism from immigration advocates.

Once implemented, asylum seekers in San Ysidro, a district in San Diego immediately north of the U.S. border with Mexico, will be processed by immigration officials and then returned to Tijuana, according to a DHS official. They will receive an 800-number to check their status and return date for the claim to be processed in 45 days.

According to a fact sheet released Thursday evening by DHS, the program is called Migrant Protection Protocols, and applies to "aliens arriving in the U.S. on land from Mexico (including those apprehended along the border) who are not clearly admissible and who are placed in removal proceedings." Unaccompanied children would not be subject to the program.

The American Immigration Lawyers' Association called the policy a "due process disaster for asylum seekers." The group says asylum seekers waiting in Mexico "would encounter substantial barriers to accessing U.S. attorneys." Asylum seekers who have legal representation are five times more likely to win their case than those who don't, according to Syracuse University's Transactional Records Access Clearinghouse.

According to the DHS fact sheet, immigrants will be "provided with a list of legal services providers in the area which offer services at little or no expense to the migrant."

The new policy is meant to address concerns that asylum seekers fail to show up for court hearings, according to Kirstjen Nielsen, the secretary of Department of Homeland Security, who announced the policy in December.

"Aliens trying to game the system to get into our country illegally will no longer be able to disappear into the United States, where many skip their court dates," wrote Nielsen in December. "Instead, they will wait for an immigration court decision while they are in Mexico. 'Catch and release' will be replaced with 'catch and return.'"

In its fact sheet, DHS said the new policy will "reduce the number of aliens taking advantage of U.S. law and discourage false asylum claims."

Under current law, asylum seekers legally enter the country at a designated port of entry, like San Ysidro, and tell an immigration officer that they are claiming asylum. They are then detained in the U.S. until they receive a "credible fear" assessment. If unsuccessful, proceedings begin to remove them from the country. If they pass, they're typically given a monitoring device, like an ankle bracelet, and a future court date.

Department of Justice data shows that 89 percent of asylum seekers were present for their court hearings in fiscal year 2017. About 93,000 migrants claimed asylum in the United States in fiscal year 2018.

It's unclear whether Tijuana is equipped to handle the immigrants. When the policy was announced, Tonatiuh Guillén, the Commissioner of Mexico's National Migration Institute, a federal agency, said the country has neither the operational or legal capacity to take in the migrants. "We can't receive them," he said, according to a translation by CBS News.

Two of the city's major shelters — Benito Juarez and Barretal — have closed in recent months, leaving even fewer beds for migrants, said Ruby Powers, an immigration attorney who spends time volunteering in Tijuana. Powers said the border city has 30 operational shelters, but the definition of "shelter" is questionable, Powers said.

"What I realized was that a shelter could be anything from a person's home, to a piece of land where people can pitch a tent," Powers said in a telephone interview with CBS News.

Questions have also been raised about safety, said Aaron Reichlin-Melnick, a policy analyst at the American Immigration Council, in a telephone interview with CBS News. Tijuana is home of a three-way cartel battle and violent crime is a part of daily life, according to the U.S. State Department.

"They're just spending their time just trying to survive in Tijuana," Reichlin-Melnick said. "We know that there are people who have been turned away from the border who have then been kidnapped, raped. There are likely people who have been murdered."