(CNN) The Pentagon announced Sunday approximately 3,750 additional U.S. forces will deploy to the southwest border to provide additional support to Customs and Border Protection.

That support includes a mobile surveillance capability through the end of September 2019 as well as placing 150 miles of concertina wire between ports of entry. The Defense Department said the total active duty forces supporting CBP at the border will be approximately 4,350.

These additional units are being deployed for 90 days.

On Thursday, CNN reported approximately 3,500 additional active duty troops will be deployed to the southern border to bolster security.

The Pentagon's decision to not reveal the size of the increase during a hearing before the House Armed Services Committee on Tuesday was slammed by the committee's chairman, Democratic Rep. Adam Smith of Washington.

"The Members of the Committee would have been extremely interested in discussing what the 3,500 troops going to the border in response to DHS's latest request will be doing there," Smith wrote in a letter to acting Secretary of Defense Pat Shanahan.

"This is a violation of the executive branch's obligation to be transparent with Congress, which oversees, authorizes, and funds its operations," Smith added.

The additional forces will allow the Department of Defense to fulfill a Department of Homeland Security request for assistance that Shanahan approved earlier last month.

President Donald Trump confirmed that additional troops would be sent via a tweet on Thursday.

"More troops being sent to the Southern Border to stop the attempted Invasion of Illegals, through large Caravans, into our Country. We have stopped the previous Caravans, and we will stop these also," Trump wrote.

Defense officials told CNN previously that the new mobile surveillance would include troops manning mobile observation posts and vehicles that would involve troops radioing CBP personnel to intercept any detected illegal activity. Under Secretary of Defense for Policy John Rood told the House Armed Services Committee Tuesday that CBP had requested the additional concertina wire "be emplaced no later than March 31."

The effort announced Sunday is separate from the potential White House-led effort to use existing Pentagon funds or personnel to help build new sections of a border wall with Mexico.