A House committee on Tuesday denied a request from Pentagon officials to move up to $1 billion to fund President Donald Trump’s promised wall on the U.S.-Mexico border.

“The committee denies this request,” House Armed Services Committee Chairman Rep. Adam Smith, D-Wa., said in a letter sent Tuesday to David Norquist, chief financial officer for the Department of Defense. “The committee does not approve the proposed use of Department of Defense funds to construct additional physical barriers or roads or install lighting in the vicinity of the United States border.”

Smith accused the Defense Department of “attempting to circumvent Congress and the American people’s opposition to the using taxpayer money for the construction of an unnecessary wall.”

“The military is paying the cost,” Smith said.

Acting Secretary of Defense Patrick Shanahan authorized the U.S. Army Corps of Engineers to begin the process of moving up to $1 billion from the Defense Department’s budget to “support (the Department of Homeland Security’s) request to build 57 miles of 18-foot-high pedestrian fencing, construction and improving roads, and installing lighting.”

The House committee's decision to deny the request could set up a legal battle over who has control over the funds, the Military Times reported.

"This is really a constitutional issue," Rick Berger, a defense research fellow at the American Enterprise Institute, told the Times. "This is a core power of the purse issue."

Trump declared an emergency on the southern border last month, after a record 35-day partial government shutdown was triggered by the battle over his request for $5.7 billion in border wall funding. Lawmakers voted to terminate the order in a joint resolution passed in the House and Senate, prompting Trump to issue his first veto.

Lawmakers failed Tuesday to secure enough votes to overrule Trump’s decision.