On Friday, Trump signed a decree that effectively suspended the granting of asylum for those who cross the border illegally, a move that could drastically slow claims at gates of entry.

U.S. military reinforced security measures Tuesday while a group of Central American citizens planning to seek asylum in the United States moved toward the country's border with Mexico, laying barbed wire and erecting barricades.

Some 400 migrants who broke away from the main caravan in Mexico City arrived in the border city of Tijuana on Tuesday by bus, according to a Reuters witness. Larger groups are expected to arrive in the coming days, human rights organizations said.

U.S. Defense Secretary Jim Mattis said he would travel to the border area on Wednesday, his first visit since the military announced that over 7,000 U.S. troops would go to the area as the caravan of mostly Hondurans has made its way through Mexico

The U.S. Customs and Border Protection (CBP) said in a statement that it would close lanes at the San Ysidro and Otay Mesa crossings from Tijuana to allow the Department of Defense to install barbed wire and position barricades and fencing. Tijuana, in the Mexican state of Baja California, is at the westerly end of the border, around 38 kilometers from San Diego, California.

The U.S. has sent over 5,200 military troops to the border to prevent the caravans’ passage two weeks ago. The American Civil Liberties Union (ACLU) recently sued the administration over its attempt to prevent people from applying for asylum.