Robert Gates, who defied expectations – and even surprised himself — by staying on as secretary of defense once George W. Bush left office, now says he expects to retire in 2011.

Gates, who turns 67 next month, tells Foreign Policy magazine that “it would be a mistake to wait until January 2012″ to step down, with just one year to go in the president’s current term. “This is not the kind of job you want to fill in the spring of an election year,” he said.