Attorney General William Barr says a new rule by the Trump administration uses "a lawful exercise of authority" to crack down on asylum claims at the U.S.-Mexico border.
The rule was published Monday and will go into effect Tuesday, blocking migrants from seeking asylum in the United States if they've traveled through another country first. Tens of thousands of migrant families from Central America travel through Mexico to the U.S. each month, many claiming asylum.
Barr says the U.S. is being "completely overwhelmed" by migration at the southern border.
Homeland Security acting Secretary Kevin McAleenan says the new rule "will help reduce a major 'pull' factor driving irregular migration."
The rule is almost certain to face a legal challenge.
Immigrant rights groups say the Republican administration's policies are a cruel effort to keep immigrants out.