In a terse two-paragraph letter, the Democrat-controlled House Armed Services Committee has rejected a plan by the Trump administration to use the U.S. Army Corps of Engineers to erect 57 miles of 18-feet-high pedestrian fencing, build and improve roads, and install lighting along sections of the southern border in Arizona and Texas.

“The committee denies this request,” says the letter signed Tuesday by Chairman Adam Smith, D-Wash. “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.”

But in its notification to Congress Monday, the Pentagon indicated it would reprogram the money without seeking congressional approval, citing a section of the U.S. code that lists “construction of roads and fences and installation of lighting to block drug smuggling corridors across international boundaries of the United States” under projects that can be funded by military counter-narcotic funds in support of U.S. law enforcement.

Smith raised the issue Tuesday during a committee hearing at which acting Defense Secretary Patrick Shanahan testified. The chairman conceded that Congress gave the Pentagon the authority to reprogram limited amounts of money so it would have some budget flexibility. But, he said, it came with a “gentleman’s agreement” that reprogramming would be done in consultation with, and the approval of, the House and Senate Appropriations and Armed Services committees.

“DoD’s recent notification of its intent to use that process to reprogram $1 billion without Congressional approval is a violation of that trust,” Smith said in a statement accompanying the release of the letter.

The Pentagon moved $1 billion out of the Army’s personnel account, which won’t be spent this year because the force missed its recruiting goal and therefore doesn't need the money for soldiers’ salaries. The money was shifted into the counter-drug account, where it can be used to support civilian law enforcement efforts, including building border barriers and other security improvements.

At the hearing, Smith warned Shanahan that defying Democrats in Congress could backfire on the Pentagon.

“The result of that likely is that the Appropriations Committee in particular would no longer give the Pentagon reprogramming authority,” Smith said. “I think that's unfortunate because they need it.”

Shanahan said the Pentagon understands what he called “the significant downsides of losing what amounts to a privilege,” noting that the risks were discussed during talks with the White House to find money for Trump’s border wall.

“By unilaterally reprogramming, it was going to affect our ability long term to be able to do discretionary reprogramming that we had traditionally done in coordination,” Shanahan said. “Those risks were weighed, and then given a legal order from the commander in chief, we are executing on that order."