WASHINGTON — The Department of Homeland Security formally asked the Pentagon on Friday to extend the mission of active-duty troops on the southwest border through the end of January.
If Defense Secretary Jim Mattis approves the request, as one Pentagon official said was expected, at least some of the military forces will spend the Christmas holidays on the border.
In a statement, Katie Waldman, a Department of Homeland Security spokeswoman, said the request would ensure the military mission “remains aligned with the current situation” on the border, where the troops have been building barriers ahead of an arriving caravan of migrants from Central America.
The troops are also backing up Customs and Border Protection officers and Border Patrol agents who might need protection — even though most of the soldiers and Marines are not carrying guns.
Defense Department officials had raised the possibility this week of extending the border mission past its current Dec. 15 end date. The new request, if approved, would keep the military forces on the border through Jan. 31.
The Trump administration deployed the roughly 5,900 active-duty troops along the border in late October, stretching between southern Texas and Southern California. President Trump had vowed to send up to 15,000 active-duty forces to the border to confront bands of migrant caravans traveling through Mexico that he described as a national security threat.
States have also deployed around 2,100 National Guard troops to the border.
The Pentagon official said the total number of active-duty troops is likely to drop in the coming weeks as units that are responsible for certain tasks — like building bases and border barriers — are sent home. The official spoke on the condition of anonymity because Friday’s request had not yet been approved.
For nearly a month, the primary job of those troops has been to string concertina wire along hundreds of miles on the border to prevent migrants from crossing into the United States anywhere but official ports of entry. The soldiers and Marines have also set up medical facilities and, under a new directive from the White House, they have started working directly alongside Border Patrol agents.
The Posse Comitatus Act, a Reconstruction-era law, prevents active-duty troops from engaging in law enforcement activities within the United States.