Washington — The Trump administration announced on Wednesday it will require Brazilian asylum-seekers to wait in Mexico for the duration of their U.S. immigration proceedings, subjecting the first non-Spanish speaking population to the controversial "Remain in Mexico" policy.

The move to send Portuguese-speaking migrants to Mexico represents the latest expansion of the Migrant Protection Protocols (MPP) program, a policy being challenged in court that has drawn scathing criticism from advocates but which the Trump administration credits for a sharp drop in apprehensions of migrants along the U.S.-Mexico border in the past seven months. Up until now, the U.S. had generally not subjected Brazilians and asylum-seekers from other non-Spanish speaking countries to the MPP program.

More than 57,000 asylum-seekers from Central America, Cuba, Venezuela and other Latin American countries who would otherwise be in the U.S. have been sent to northern Mexico, where they are often stranded in overcrowded shelters and squalid makeshift encampments, including in crime-ridden cities like Ciudad Juárez and Matamoros, located in a region the U.S. government warns American travelers not to visit due to rampant violence.

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The Trump administration has hailed the policy as a successful tool in curbing migration and Wednesday's announcement is likely designed to deter U.S.-bound Brazilian migrants, who typically journey through Central America and Mexico to reach the U.S. southern border.

In a statement announcing the move, the Department of Homeland Security said the number of Brazilians reaching the U.S.-Mexico border "tripled in just the last year." Border Patrol apprehended more than 6,300 Brazilians between September and December 2019, according to Customs and Border Protection statistics that showed people from Brazil made up the fifth largest group of apprehensions in that time span after migrants from Mexico, El Salvador, Honduras and Guatemala.

"Having an outlet for (Brazilians) to wait outside the U.S. for their immigration hearings is super-helpful!" Ken Cuccinelli, the second-highest ranking official at DHS, wrote on Twitter, thanking the government of Mexico for accepting the change in policy.

Today is the one-year anniversary of the first person actually waiting in Mexico under MPP, aka, the remain in Mexico program. And on today's 1 year anniversary, the first Brazilians were returned to Mexico to await their U.S. Immigration hearing. Adding Brazilians is BIG! — Acting Deputy Secretary Ken Cuccinelli (@HomelandKen) January 29, 2020

BuzzFeed News and Reuters first reported that officials were planning to subject Brazilians to the MPP policy.

Despite the praise from the Trump administration, advocates and even some of the asylum officers implementing the program have strongly denounced the Remain in Mexico policy, saying it violates international obligations against returning migrants seeking refuge to dangerous places. The group Human Rights First has denounced hundreds of reported kidnappings and assaults.

A CBS News series last summer detailed the due process concerns about the policy, which makes it extremely difficult for migrants to secure U.S.-based lawyers generally needed for successful asylum claims. According to data by researchers at Syracuse University, only about 4% of migrants in the program have had lawyers represent them in proceedings in the U.S. — which, for many migrants, now occur inside makeshift tent-like courts in the Rio Grande Valley.

Out of nearly 30,000 completed cases in the program, only 187 migrants have been granted asylum or some other form of protection, according to Syracuse's Transactional Records Access Clearinghouse (TRAC). Under an expansion of the policy in early January 2020, some asylum-seekers returned by the U.S. to Mexico will have to travel more than 340 miles by car through territory where cartels often vie for control of the drug trade to attend hearings in a U.S. immigration court.