Three unnamed U.S. officials told NBC News that DHS wants the troops to upgrade 160 miles of fencing along the border.

SHOW TRANSCRIPT

More U.S. troops might be deployed to the U.S.-Mexico border to upgrade 160 miles of fencing.

Three unnamed U.S. officials told NBC News the Department of Homeland Security made the request for additional troops to Acting Secretary of Defense Patrick Shanahan.

Now, the Department of Defense is not affected by the partial government shutdown, and the cost of any fence construction would reportedly come out of the Pentagon's annual budget.

The Trump administration announced plans to deploy thousands of active-duty troops to the border back in late October, in response to migrants who were traveling north through Mexico at the time.

Those troops have been supporting U.S. Customs and Border Protection efforts by helping with surveillance, reinforcing barriers, and providing medical support and temporary housing.

Now some of those troops have reportedly come home, but the roughly 2,300 who are still at the southern border are scheduled to remain there until the end of January.

NBC News' sources say this recent DHS request could extend the mission through September, though. It would be up to the Pentagon to decide if the troops it deploys are active-duty or members of the National Guard.