There have been roughly 5,400 active-duty troops along the border in recent weeks, installing wire barriers and protecting border patrol agents in California, Arizona and Texas.
Defense Secretary Jim Mattis approved plans to extend the deployment of active-duty U.S. troops at the southern border with Mexico until Jan. 31.
President Donald Trump ordered the deployment of troops in response to a caravan of Central American migrants moving toward the U.S. border.
The number of migrants has been declining and the military has finished much of the wire barrier placement.
Officials say there is less need for combat engineers and helicopter transport crews. But many of the military police will remain.
The officials spoke anonymously because they weren’t authorized to speak publicly.