SAN DIEGO - The Trump administration on Friday will start forcing some asylum seekers to wait in Mexico while their cases proceed through U.S. courts, an official said, launching what could become one of the more significant changes to the immigration system in years.

The changes will be introduced at San Diego's San Ysidro border crossing. San Ysidro is the nation's busiest crossing and the choice of asylum seekers who arrived to Tijuana, Mexico, in November in a caravan of more than 6,000 mostly Central American migrants.

The U.S. Department of Homeland Security (DHS) said the Migrant Protection Protocols will return some asylum seekers to Mexico as they wait for their cases to be processed in the U.S. The announcement said Mexico will provide the migrants will all appropriate humanitarian protections for the duration of their stay.

DHS said the U.S. is “facing a security and humanitarian crisis on the Southern Border” and that is why it has implemented the MPP “to address the crisis and execute our missions to secure the border, enforce immigration and customs laws, facilitate legal trade and travel, counter traffickers, smugglers and transnational criminal organizations, and interdict drugs and illegal contraband.”

“Families and individuals traveling to the border are not a national security crisis,” said Margaret Huang, executive director of Amnesty International USA. “They are people like you and me, except that many have left their home to seek protection form persecution and violence. We must not abandon those who have lost everything and are trying to rebuild their lives.”

Huang is a member of an international delegation traveling to the U.S.-Mexico border to observe the impact of the U.S. policy on migrants.

DHS said MPP will “discourage individuals from attempting illegal entry and making false claims to stay in the U.S., and allow more resources to be dedicated to individuals who legitimately qualify for asylum.”

DHS said it is “working closely” with the Justice Department “to streamline the process.” The agency added that it is also looking to “conclude removal proceedings as expeditiously as possible.”

The policy, which is expected to face a legal challenge, may be expanded to other crossings. It does not apply to children traveling alone or to asylum seekers from Mexico.

The plan calls for U.S. authorities to bus asylum seekers back and forth to the border for court hearings in downtown San Diego, including an initial appearance within 45 days.

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.

U.S. officials also will begin processing only about 20 asylum claims a day at the San Diego crossing but plan to ramp up to exceed the number of claims processed now, which is up to 100 a day, the official said.

Migrants from Cuba, Venezuela and Central America FILE - Migrants from Cuba, Venezuela and Central America queue at the Paso del Norte International Bridge in Ciudad Juarez, Chihuahua state, Mexico, to cross the border and request political asylum in the United States, Jan. 9, 2019. FILE - Migrants from Cuba, Venezuela and Central America queue at the Paso del Norte International Bridge in Ciudad Juarez, Chihuahua state, Mexico, to cross the border and request political asylum in the United States, Jan. 9, 2019.

?'Credible fear'

The policy could severely strain Mexican border cities. U.S. border authorities fielded 92,959 "credible fear" claims — an initial screening to have asylum considered — during a recent 12-month period, up 67 percent from a year earlier. Many were Central American families.

The "Remain in Mexico" policy is President Donald Trump's latest move to reshape immigration policy, though it may prove temporary. Other major changes have been blocked in court, including a ban on seeking asylum for people who cross the border illegally from Mexico and generally dismissing domestic and gang violence as grounds for asylum.

It is also an early test of relations between two populist presidents — Trump and Mexico's Andres Manuel Lopez Obrador, who took office Dec. 1.

Mexican officials did not immediately respond to requests for comment Thursday.

Roberto Velasquez, spokesman for Mexico's foreign relations secretary, emphasized earlier this week that there would be no bilateral agreement and that Mexico was responding to a unilateral move by the United States. He said in an interview that discussions covering "a very broad range of topics" were aimed at preparing Mexico for the change.

Broad outlines of the plan were announced Dec. 20, but details were not revealed until Thursday. Mexico said last month that people seeking asylum in the U.S. would get temporary humanitarian visas while their cases were settled in the U.S., which can take years, and could seek permission to work in Mexico.

Migrants from Honduras, part of a caravan of thous FILE - Migrants from Honduras, part of a caravan of thousands from Central America trying to reach the United States, jump the fence to cross it illegally into San Diego County, U.S., taken from the border wall in Tijuana, Mexico, at right, Jan. 16, 2019. FILE - Migrants from Honduras, part of a caravan of thousands from Central America trying to reach the United States, jump the fence to cross it illegally into San Diego County, U.S., taken from the border wall in Tijuana, Mexico, at right, Jan. 16, 2019.

Mexico has started issuing humanitarian visas to Central Americans as another major caravan makes its way through the southern part of the country.

While illegal crossings from Mexico are at historically low levels, the U.S. has witnessed a surge in asylum claims, especially from Central American families. Because of a lack of family detention space and a court-imposed 20-day limit on detaining children, they 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.

Tijuana's effects

It's not clear if Central Americans will be deterred from seeking asylum in the U.S. if they have to wait in Tijuana, a booming city with plenty of jobs. Tijuana doesn't come close to matching the U.S. on wages, and asylum seekers generally have far fewer family ties there than they do in the U.S.

Incoming Foreign Relations Secretary Marcelo Ebrard has said Mexico will coordinate with the U.S. on the policy's mechanics, which would ensure migrants access to information and legal services. Ebrard said Dec. 24 that he wanted more information to ensure "orderly and secure" protocols.

Rafael Fernandez de Castro, director of the University of California-San Diego's Center for U.S.-Mexico Studies, said last week that Mexico had not fully considered the impact on Mexican border towns.

"This could have lasting repercussions for Mexican border cities," Fernandez de Castro said. "We have to assess the potential numbers and how to help them stay healthy. We don't have that assessment."

VOA contributed to this report.