"I spent a long time hoping the question would never be popped ... and then yesterday, it became a reality," Gates told reporters. "It should go without saying that I have no intention of being a caretaker secretary."

Gates said he has not registered with a political party, but considers himself a Republican, and noting that, until Monday, all of his senior appointments had been under Republican presidents.

He said that in the 60 years that the job of secretary of defense has existed, he is the first to be asked by an incoming president of either party to keep the job, and thanked President-elect Barack Obama "for his confidence in me."