Pres. Jimmy Carter, left, meets with Secretary of Energy James Schlesinger, Secretary of Treasury Michael Blumenthal, Undersecretary of Treasury Anthony Solomon, and U.S. ambassador to the economic summit Henry Owen during their flight from Washington, D.C. to Anchorage, Saturday, June 23, 1979. (AP Photo)

A Washington think tank confirms James Schlesinger has died.

Schlesinger was Secretary of Defense from 1973 to 1975 under Presidents Richard Nixon and Gerald Ford.

He became America's first Secretary of Energy under Jimmy Carter.  

Earlier in his career he was a top White House budget official, chairman of the Atomic Energy Commission and director of the Central Intelligence Agency.

Schlesinger died at a hospital in Baltimore, he was 85. The cause of death cardiac arrest. Schlesinger had been suffering from pneumonia. 

The Center for Strategic and International Studies, where Schlesinger was a trustee, confirmed his death Thursday.  

Schlesinger graduated from Harvard -- getting a degree in Economics -- and took the top spot at the Pentagon in 1973 in an attempt to boost the Defense Department's declining budget and morale after the Vietnam War. 

Schlesinger is credited with shifting the administration's thinking on nuclear weapons, advocating for and a flexible response of limited strikes to replace the deterrence policy of mutually assured destruction.

After leaving office, Schlesinger worked for Lehman Brothers, Kuhn Loeb Inc. as a senior adviser and was consulted numerous times on defense issues during George W. Bush's presidency.