"I think sometime in 2011 sounds pretty good," Gates told Foreign Policy magazine. "It would be a mistake to wait until January 2012," he said, because that would force President Barack Obama to fill the defense post in the heat of his re-election campaign.
"I just think this is not the kind of job you want to fill in the spring of a presidential election," Gates said.
Gates, who turns 67 next month, will lead a strategic review on the Afghan war and the decision to begin withdrawing U.S. troops in July 2011. In December, the Pentagon is expected to oversee the move to allow gays to serve openly in the military.
White House spokesman Bill Burton told reporters in Wisconsin Gates had agreed to stay in the position longer than he had intended.
"The president is gratefully thankful for that service, but any announcement will come from him," Burton said during Obama's visit to a Wisconsin clean-energy plant that received a $1.3 million federal stimulus loan.
Noting Gates has said publicly he could retire next year, Burton said, "It's not a surprise to see him discussing his plans to move on."
The New York Daily News reported Monday potential Gates successors include Michele Flournoy, the Defense Department policy undersecretary who would become the first woman to head the department, CIA Director Leon Panetta and former Navy Secretary Richard Danzig, who advised Obama on national security during the president's 2008 campaign.