A bipartisan group of senators want the Trump administration to immediately modify the new civilian hiring freeze because it is "extremely inefficient" and poses a threat to military readiness.

Sens. Mike Lee, R-Utah, Tim Kaine, D-Va., and seven other senators sent the letter to Kathleen McGettigan, acting director of the Office of Personnel Management, which is in charge of implementing the freeze imposed by Trump on Jan. 23.

The freeze excludes military personnel, but it significantly slows hiring of the civilians who augment and work alongside the military.

"It has come to our attention that, due to implementation guidance on the Presidential Memorandum, waivers for civilian hiring at military depots, shipyards, plants and arsenals are being issued by service secretaries on a job-by-job basis," the senators wrote. "This practice is extremely inefficient, impractical, and should be changed immediately. By the very nature of the work done at these facilities, commanders and managers must persistently address vacancies and new needs in the workforce to adapt to the constantly fluctuating demands of the warfighter."

The senators called on OPM to work "expeditiously" with the Department of Defense to clarify the hiring freeze.

They said if the hiring freeze is not modified to allow the military discretion to hire civilian military workers, "readiness goals" set by new Secretary of Defense James Mattis, "will be much harder to achieve."