Prof Henry Louis Gates is a prominent Harvard scholar
The US president has said police acted "stupidly" when they arrested a black Harvard scholar outside his own home.
Prof Henry Louis Gates was held last week in Cambridge, Massachusetts, home to the top university where he teaches.
Barack Obama said the US had a long history of African-Americans being disproportionately stopped by police.
Officers were called to Prof Gates's house after a woman reported seeing two black males - the professor and his driver - trying to force entry.
Although the exact facts of the incident are disputed, Prof Gates was asked to provide the officer with identification. He was then asked to step outside his house and was arrested.
Mr Obama said: "I think it's fair to say, number one, any of us would be pretty angry.
"Number two... the Cambridge police acted stupidly in arresting somebody when there was already proof that they were in their own home."
President Obama: "The Cambridge police acted stupidly in arresting somebody when there was already proof that they were in their own home"
An initial disorderly conduct charge was dropped and Cambridge police called the arrest "regrettable and unfortunate".
Mr Obama said federal officials should work with local police to "improve policing techniques so that we're eliminating potential bias".
He said that when he was in the Illinois state legislature, he had worked towards a racial profiling bill because there was indisputable evidence that African-Americans and Hispanics were being stopped disproportionately.
"And that is a sign, an example of how race remains a factor in the society," he said.
Prof Gates has said he was "outraged" by the arrest and called the officer, Sgt James Crowley, a "rogue policeman". Sgt Crowley has refused to apologise.
During the confrontation between the two men, the 58-year-old professor reportedly said: "This is what happens to black men in America."
His lawyer said Prof Gates had just returned from a trip overseas and, upon arriving at the property with a driver, found his front door jammed and had to force it open.
By the time police arrived at the house, he and the driver had managed to get inside the property.
According to police, Prof Gates shouted at the officer and accused him of racial bias.
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