It is unclear why Zakheim is leaving his job at a time when the Pentagon is defending its fiscal 2005 budget submission to lawmakers, but Pentagon sources say that reports he intended to leave the department have been circulating since last fall.
Zakheim previously served as the deputy undersecretary of Defense for planning and resources in the Pentagon's policy shop.
Most recently he was corporate vice president of System Planning Corp., a technology, research and analysis firm based in Arlington, Va.
He also served as chief executive officer of SPC International Corp., a subsidiary specializing in political, military and economic consulting. During the 2000 presidential campaign, Zakheim served as a senior foreign policy adviser to then-Gov. George W. Bush.