Mattis approves deployment of National Guard troops at US-Mexico border

US Defense Secretary James Mattis has signed a memo according to which the National Guard will deploy up to 4,000 troops to the U.S.-Mexico border.

According to the Hill, the move permits the use of the Pentagon money for up to 4,000 National Guard personnel to support the Department of Homeland Security's "southern border security mission while under the command and control of their respective governors through September 30, 2018."

The memo reportedly further states that the troops will not be used for law enforcement or interaction with immigrants unless Defense Secretary James Mattis approves it, and that the troops will be armed only if required for self-defense.

It will be valid for the current budget year, which ends on 30 September, however, the memo does not say how much the mission will cost.

The initial deployment of 500 will include soldiers and airmen.

"Always Ready, Always There! Moving up to 500 #NationalGuard troops immediately on the SW border security mission. Vehicles, equipment & helicopters on the way tonight," National Guard Bureau Chief Gen. Joseph Lengyel wrote on Twitter.