U.S. President Barack Obama Friday sought to quell a controversy involving remarks he made about the controversial arrest of a prominent African-American scholar in Massachusetts last week.  At his news conference on Wednesday, the president said police acted stupidly in arresting Harvard University Professor Henry Louis Gates.  Now the president says he should have chosen his words more carefully.

Professor Gates was arrested at his home in Cambridge, Massachusetts, last week after a neighbor saw Gates trying to pry open his front door and mistakenly thought a burglary was in progress.

Cambridge Police Sergeant James Crowley said Gates got angry and accused him of racial bias after the officer asked Gates for identification while standing in his house.  Gates was arrested for disorderly conduct, but the charge was later dropped.

At his news conference Wednesday, President Obama said that although he did not know all the facts, he thought the Cambridge Police acted stupidly in arresting Gates.

On Friday, the president called Sergeant Crowley to talk about the incident, and then took the unusual step of appearing unannounced before reporters at the White House to say he should have chosen his words more carefully in talking about the incident.

"And because this has been ratcheting up, and I obviously helped to contribute ratcheting it up, I want to make clear that in my choice of words I unfortunately gave an impression  that I was maligning the Cambridge Police Department or Sergeant Crowley specifically, and I could have calibrated those words differently, and I told those words to Sergeant Crowley," he said.

The President also telephoned Professor Gates on Friday and the White House said the two men had a positive discussion.

The controversy over the Gates arrest has refocused national attention on the issue of racial profiling.  Civil rights leaders have complained for decades that police often unfairly target minorities in traffic stops and criminal investigations.

Gates spoke about the incident on the Gayle King show on XM satellite radio. "People who want to protect the police or who are afraid of criminals, and I am afraid of criminals, are looking for something that I could have done to justify Sergeant Crowley's action.  There is nothing I could have done to justify Sergeant Crowley's action," he said.

Sergeant Crowley told Boston television station WHDH that he followed police procedure in asking Gates for identification. "He was the one who was being provocative.  This was not a back and forth exchange of banter or arguing, this was one-sided.  I really did not want to have to take such a drastic action because I knew that it was going to bring a certain amount of attention, unwanted attention, on me."

Crowley is a respected veteran with the Cambridge Police department who has taught police recruits how to avoid racial profiling.

Police unions in Massachusetts rallied to Crowley's defense Friday, and several union officials demanded that the president apologize for his earlier comment.

After his call with Sergeant Crowley on Friday, the president said that it appeared that both men could have done more to prevent the incident from escalating. "I continue to believe, based on what I have heard, that there was an over-reaction in pulling Professor Gates out of his home to the station.  I also continue to believe, based on what I heard, that Professor Gates probably overreacted as well," he said.

Mr. Obama said he discussed with Sergeant Crowley the possibility of having the officer and Professor Gates join him at the White House for a beer.

The president also expressed the hope that some good might eventually come of the Gates incident.

"My hope is that as a consequence of this event, this ends up being what is called a teachable moment where all of us instead of pumping up the volume spend a little more time listening to each other and focus on how we can generally improve relations between police officers and minority communities, and instead of flinging accusations, we can all be a little more reflective in terms of what we can contribute to more unity.  Lord knows we need it right now," he said.

The president's comments about the Gates case have been a major distraction for the White House in recent days, and had shifted attention away from Mr. Obama's efforts to build public support for his top domestic priority-reforming the U.S. health care system.