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WASHINGTON — Congressional leaders from both parties told Acting Defense Secretary Patrick Shanahan on Tuesday that the Trump administration's plan to use Pentagon funds to build a border wall will hurt readiness, and demanded justification for using the funds.

"We fear that reprogramming funding intended for military construction projects and counterdrug activities will come at the expense of troop readiness and Department-wide efforts to address the military's aging infrastructure," wrote Reps. John Garamendi, D–Calif., and Doug Lamborn, R–Colo., the chair and ranking member of the Readiness Subcommittee of the House Armed Services Committee, in a letter to Shanahan.

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The congressmen asked Shanahan to provide specifics by Friday about which military construction programs will be affected and to explain why using the funds to build a border wall "is necessary to support our armed forces."

The city of Ciudad Juarez in Mexico seen through the border fence from El Paso, Texas, on Feb. 23, 2019. Pablo Martinez Monsivais / AFP - Getty Images

In spring 2018, Pentagon officials reported that the Department of Defense facility maintenance backlog exceeded $116 billion. "We currently have an underfunded maintenance backlog exceeding $116 billion; 23 percent of the department's facilities are in poor condition," Lucian Niemeyer, assistant secretary of defense for energy, installations and environment told the House Armed Services Committee last year, adding that 9 percent of DOD facilities are in "failing condition."

Click here to read the letter

The Congressmen argue the money should be used to support the military. "These investments should go to supporting new weapon systems, replacing aging facilities, and improving the readiness and quality of life of our troops and their families as originally intended," said the letter.

The Department of Defense has roughly $1 billion appropriated for counternarcotic missions and drug interdiction for FY19. Garamendi and Lamborn said that the administration has asked for $2.5 billion to be pulled from this "284" funding for the wall, meaning the Pentagon will have to divert money from elsewhere beyond the 284 funding to find the $2.5 billion. "We have serious concerns about the impact any reprogramming may have on readiness."

The 284 funding allows the Pentagon to support construction of roads and fences to block drug smuggling corridors across international borders. The congressmen also ask for justification of "how the location is a drug smuggling corridor and fencing is necessary."

A Defense Department officials confirmed Shanahan had received the letter.