The Pentagon has implemented a civilian hiring freeze affecting defense agencies, Defense News reported late Thursday. The move comes following a congressional order after years of debate and lobbying to reduce the number of staff positions at the Pentagon.

“We have instructions, both internal and from the Congress to hold down civilian [jobs] commensurate with drawdown in the military, and we recognize that mandate,” Pentagon Comptroller Mike McCord said Tuesday.

Former Secretary of Defense Chuck Hagel issued a memorandum in 2013 calling for a 20 percent staff reduction, a move that is now being overseen by current Secretary of Defense Ash Carter.

“In this period of additional downward pressure on defense spending, we must continue to reduce our headquarters’ budgets and staffing,” Hagel said in the 2013 memorandum.

The civilian hiring freeze that went into effect Sunday affects the office of the secretary of defense, defense agencies and field activities. Deputy Secretary of Defense Bob Work ordered the freeze, which covers vacant civilian positions, Feb. 23 as part of the Pentagon’s so-called “delayering” process. Work also raised the target reduction goal to 25 percent.

The hiring freeze will be lifted once agencies have presented their plans and gained approval from a senior review panel with the goal of obtaining a better portrait of the number of employees needed in agencies. An exception has been made for positions that are critical to fulfill mission requirements.

The staff reduction came at the same moment as a 2013 federal spending cap. While Arizona Sen. John McCain has vocally supported the staff reductions, he has challenged Pentagon spending cuts.

“Our nation will deploy young Americans into battle without sufficient training or equipment to fight a war that will take longer, be larger, cost more and ultimately claim more American lives than it otherwise would have,” McCain said earlier in March, Time reported.