The Pentagon announced Friday that it would direct an additional 1,000 troops to the U.S.-Mexico border to install barbed wire along existing border fences.

Defense officials said at a news briefing that the total size of the U.S. deployment of troops to the southern border would reach 6,000 by March 1, with 140 miles of additional concertina wire to be installed.

“That mission has evolved,” a senior defense official said. “We are now transitioning to supporting [areas] between the ports of entry. We’re laying down another 140 miles of concertina wire — [we’re] about 30 percent done with that — as well as providing a ground-based detection and monitoring mission in support of [Customs and Border Protection]."

"Our numbers right now total are about 5,000. They’ll increase to about 6,000 by March 1," the official added.

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The additional 1,000 troops are active-duty and are primarily being sent to support the two missions at the border, the official said.

“One is wire placement and the other is the detection and monitoring between the ports of entry," they said.

"We are not just sending people down there unless there’s a valid requirement and then we try to match, as best we can, resources to the requirement with as much specificity as possible. And if we don’t need those people then we’ll move them somewhere else."

The news came as Pentagon officials on Friday also refused to say whether the Defense Department would seek congressional approval to appropriate billions of dollars for President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's project to construct a wall along the border.

“It has been the practice of the Department of Defense to request approval and it’s not required by law,” an official told reporters when asked whether the department would move forward without congressional approval.

The president declared a national emergency earlier this month in an attempt to allocate funds for the border wall after Democrats refused to provide the full $5.7 billion the White House had requested for the wall in a deal to avert another government shutdown.

Democrats have introduced a resolution in the House to block the emergency declaration, which the president has vowed to veto if it reaches his desk.

— Ellen Mitchell contributed