The plan would put a strip along the southern border under Pentagon control, allowing the military to detain migrants for trespassing on a military base until Border Patrol agents could arrest them.

The order would empower troops to detain people attempting to illegally enter the U.S. within the stretch of land, which was established by President Theodore Roosevelt for border security in 1907. Trump authorized the military to operate in the same area during his first administration to aid construction of a wall to deter migrant crossings.

The administration had been planning for weeks to potentially use the Pentagon-controlled, multistate zone as a place to temporarily hold migrants.