WASHINGTON - Trying to tamp down an uproar over race, President Barack Obama said Friday he used an unfortunate choice of words in commenting on the arrest of black scholar Henry Louis Gates Jr. and could have "calibrated those words differently."

The president said he had telephoned the white policeman who arrested Gates, and he said the conversation confirmed his belief that the officer was a good man and an outstanding officer.

The president caused a stir when he said at a prime-time news conference earlier this week that Cambridge, Mass., police had "acted stupidly" by arresting Gates, a friend of the president's, for disorderly conduct.

On Friday, Obama made an impromptu appearance at the daily White House briefing in an effort to contain the controversy. He said he continued to believe that the both the officer, Sgt. James Crowley, and Gates had overreacted during the incident, but the president also faulted his own comments.

"This has been ratcheting up, and I obviously helped to contribute ratcheting it up," he said. "I want to make clear that in my choice of words, I think I unfortunately gave an impression that I was maligning the Cambridge police department and Sgt. Crowley specifically. And I could've calibrated those words differently."

The incident began when police went to Gates' home last week after a passer-by reported a potential break-in. It turned out that Gates had tried to jimmy open his own door, which was stuck, and there was no intruder. Gates protested the police actions and was arrested, although the charges have since been dropped.