WASHINGTON — In a new letter to the secretary of the US Air Force, Sen. John McCain, R-Ariz., says the service is playing a "shell game" with staff figures in order to avoid required reductions in headquarter staff levels.

McCain, the chairman of the Senate Armed Services Committee, posted online the text of his letter to Secretary Deborah Lee James on Wednesday.

At issue is a 2013 memo from then-Secretary of Defense Chuck Hagel directing the services to reduce their headquarters staff level by 20 percent. Those reductions were to be overseen by Ash Carter, then the deputy defense secretary and now Hagel's successor as secretary of defense.

The Air Force has publicly said it is taking the lead in reducing headquarters staff, with James telling a Senate hearing last week that the Air Force has already reached that 20 percent reduction threshold.

In his letter, however, McCain takes issue with the service's claim.

"After touting the speed at which the Air Force had achieved a 20-percent headquarters reduction, you later conceded that none of the Air Force civilians that were part of that reduction were actually removed from the payroll of the Air Force," McCain wrote.

Instead, the senator wrote, the service created the reductions by shifting various groups around on paper. That includes turning the Air Force Intelligence, Surveillance, and Reconnaissance Agency into the Twenty-Fifth Air Force, a numbered Air Force operating under Air Combat Command.

"The conduct of the Air Force in response to this guidance seems to have produced no actual staff reductions and yielded no actual savings," McCain continued. "The Senate Armed Services Committee has received no reprogramming request from the Air Force for savings generated in the headquarters budget. In reality, the Air Force pursued a shell game that simply moved money to fund the same positions elsewhere in the service."

At the conclusion of his letter, McCain said his committee will continue to monitor the staff reduction issue "closely."

An Air Force spokeswoman said officials would respond to the letter as quickly as possible, and added that the service "looks forward to explaining its efforts in striving to meet the 20 percent Management Headquarters Reduction."

The relationship between the Air Force and McCain is being closely watched by the defense world. The service is already in his doghouse due to the ongoing attempt to retire the A-10 Warthog, which McCain has fiercely defended.

Twitter: @AaronMehta