U.S. officials say the Pentagon will begin deploying as many as 1,500 active duty troops to help secure the southern border in the coming days.

It was not immediately clear what units and service branches would be tapped for the deployment, but the announcement comes amid the Trump administration's executive actions directing a comprehensive military border mission.

The order will deploy 1,500 troops to build physical barriers, but they will not be used for law enforcement, a military official says.