SAN FRANCISCO — The American Civil Liberties Union has filed a federal lawsuit challenging a new Trump administration policy barring people who cross the U.S.-Mexico border illegally from seeking asylum.

The lawsuit, filed in San Francisco Friday, alleges the “asylum ban” is illegal and targets undocumented immigrants fleeing persecution who don’t always have the resources to cross the border at ports of entry.

“Individuals who arrive at the southern border seeking protection in the United States through the asylum process are fleeing some of the most dangerous countries in the world,” the lawsuit said. “Those who leave often are running from life-or-death situations, leaving everything behind to make a dangerous journey.”

Trump signed a proclamation Friday suspending entry into the U.S. from the border, saying, “our system is being overwhelmed by migration through our southern border. Crossing the border to avoid detection and then, if apprehended, claiming a fear of persecution is in too many instances an avenue to near-automatic release into the interior of the United States.”

The ACLU, the Southern Poverty Law Center, and Center for Constitutional Rights filed the lawsuit on behalf of the East Bay Sanctuary Covenant, Al Otro Lado, Innovation Law Lab, and the Central American Resource Center in Los Angeles.