Washington, Dec 1 (IANS): The US Department of Homeland Security (DHS) has formally requested the Pentagon to extend the deployment of active-duty troops on the southern border, potentially extending their deployment 45 days beyond the original deadline of December 15.

"Given the ongoing threat at our Southern border -- today the Department of Homeland Security submitted a request for assistance to the Department of Defence to extend its support through January 31, 2019," Department of Homeland Security spokeswoman Katie Waldman told CNN on Friday.

"This request refines support to ensure it remains aligned with the current situation, the nature of the mission, and (Customs and Border Protection) operational requirements."

The Pentagon confirmed a receipt of the request but said that Secretary of Defence James Mattis was yet to sign it.

There are currently some 5,600 troops at the border, divided among Texas, California and Arizona.

President Donald Trump sent the troops after spending the weeks leading up to the midterm elections decrying a procession of migrants that was still thousands of miles from the US border.

Last week, Trump granted the troops new powers to aid in "crowd control, temporary detention and cursory search" while protecting Customs and Border Protection personnel from the migrants, should they engage in violence.

The deployment's extension means the Pentagon's initial cost estimate of $72 million for the border deployment is likely to increase as that estimate was based on the mission ending on December 15.