WASHINGTON (Reuters) - The U.S. House of Representatives Armed Services Committee on Tuesday denied the Pentagon’s plan to shift $1 billion to build a wall on the U.S. border with Mexico, a move that while largely symbolic, highlights the concern lawmakers have about using the defense budget to pay for the wall.

Chairman of the House Armed Forces Committee Adam Smith (D-WA) awaits the arrival of Acting U.S. Secretary of Defense Patrick Shanahan and Chairman of the Joint Chiefs of Staff General Joseph Dunford to testify on the Fiscal Year 2020 National Defense Budget Request from the Department of Defense on Capitol Hill in Washington, U.S., March 26, 2019. REUTERS/Joshua Roberts

Acting Secretary of Defense Patrick Shanahan announced on Monday that the Department of Defense had shifted $1 billion from other military construction projects to build part of the barrier along the southern border.

Democratic Representative Adam Smith, the committee’s chairman, said the panel did not approve the proposed use of Pentagon funds.

His stance could end up being symbolic, as the Pentagon insists it has the authority to shift the money. However, it could prompt Congress to change the law to prevent presidents from taking similar action in the future.

A court battle over the issue is also likely.

“The committee denies this request. The committee does not approve the proposed use of Department of Defense funds to construct additional physical barriers and roads or install lighting in the vicinity of the United States border,” Smith said in a letter to the Department of Defense.

During a House Armed Services Committee hearing that was in progress when Smith released his statement, Shanahan acknowledged that the decision to move money could impact the Pentagon’s ability to reprogram funds in the future.

“It was a very difficult discussion and we understand the significant downsides of losing what amounts to a privilege,” Shanahan said.

Shanahan’s move to shift military dollars to pay for the wall without consulting Congress could lead lawmakers to cut off the Pentagon’s authority to reprogram funds, something Smith hinted at during the hearing.

Lawmakers from both political parties were critical of the decision to use military funds for the wall.

“Changing decades of reprogramming practice is going to have difficult consequences for the whole government, but especially for the Department of Defense,” Representative Mac Thornberry said in the hearing.

The House failed on Tuesday to override President Donald Trump’s first veto of the “national emergency” he declared last month to build a U.S.-Mexico border wall that Congress has not funded.

Smith told the hearing that Trump’s proposed $750 billion defense budget would not pass as it was proposed. That budget included $100 billion in a “slush fund” meant to fund ongoing wars but which the Pentagon intends to use to boost the amount of money it has available to avoid budget caps.