"Today, DHS submitted a request for assistance to the Department of Defence to extend its support through January 31, 2019," Davis said on Friday. "This request refines support to ensure it remains aligned with the current threat, the nature of the mission, and CBP [Customs and Border Protection] operational requirements."
The active duty military personnel were deployed to the US border with Mexico in October to assist CBP upon the arrival of migrant caravans from Central America.
The Defence Department is reinforcing priority ports of entry in the border states of Texas, Arizona and California. The Pentagon has deployed engineers and military police units, as well as troops who specialize in aviation, medical treatment and logistic.
The current cost of deploying American active-duty troops to the US-Mexico border in support of immigration enforcement amounts to at least $72 million, Department of Defence spokesperson Col. Rob Manning said in a statement.