The Department of Defense (DOD) moved more than $146 billion over six years from its war readiness fund to pay for basic military operations.

Between 2009 and 2015, the DOD spent $146.9 billion designated for emergency war readiness on general operations, according to a Government Accountability Office (GAO) report released Tuesday. The report confirmed what many in Congress see as a misuse of a controversial discretionary account.

“GAO found that DOD used its authorities to realign about $146.9 billion of its funding from fiscal years 2009 through 2015,” the GAO said.

The Overseas Contingency Operations (OCO) fund, sometimes panned as the Pentagon’s slush fund, is a separate funding mechanism from the DOD’s base operations and maintenance account. As the name suggests, the fund is designed to give the Pentagon flexibility to deal with foreign threats while waiting for congressional appropriations. The fund is not subject to sequestration or budget caps like the Pentagon’s base budget.

The Pentagon took money from the OCO account and used it to bolster its base operation fund, or what are referred to as Operation and Maintenance accounts, the GAO found.

The base operation budget represents the largest bloc of the defense accounts, which cover things like payroll, training, upkeep of military bases, maintenance of weapons, ammunition, administrative and management costs, and advertising for recruitment. The base budget does not include appropriations for new weapons systems, military missions, or research and development.

The DOD is not required to separate spending on basic operations from OCO spending. The GAO recommends revising the policy.

“By revising its guidance to require congressional reporting on O&M base obligations for each account in these materials and reports, DOD could provide complete information to assist Congress in better understanding and overseeing DOD’s full funding needs for O&M base,” the GAO said.

Pentagon officials disagreed with the GAO’s recommendation, saying separating the accounts would be “very difficult and labor intensive,” in an official response included in the report.

GAO conducted the report after the appropriations committees in both the House and Senate “on several occasions expressed concern that DOD relies on a portion of its OCO appropriations to fund O&M programs and activities that began in response to contingency operations but have continued after these operations ended,” the report said.

Sen. John McCain, chairman of the Senate Committee on Armed Services, has criticized the Pentagon’s use of the OCO fund. He has also said that if Congress wants stop the DOD from using it, Congress need to increase the military’s base spending.

The report comes as Congress is about to tackle the 2017 National Defense Authorization Act after the summer recess. Republicans have requested additional funding for the military’s base budget, but some see the OCO as a likely compromise.

“More OCO is going to win,” Mackenzie Eaglen, fellow at the American Enterprise Institute, told The Hill. “Period. Take it Vegas. It’s done. It won’t be as high as the GOP is hoping, but it’s going to be more.”

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