US President Barack Obama says there are no plans to revoke Bill Cosby's Medal of Freedom amid allegations that the comedian raped as many as 40 women.

Obama said there is no precedent or mechanism to revoke the honour, which Cosby was awarded in 2002.

The president declined to discuss any specific aspects of Cosby's case.

However, Obama did say that giving someone a drug and then having sex with them without their consent should be considered rape.

"I think this country, any civilized country, should have no tolerance for rape," Obama told reporters on Wednesday.

 Cosby admitted during a court case that he had obtained Quaaludes - a sedative - to give to women with whom he wanted to have sex.

Dozens of women have come forward and said they were drugged and raped by Cosby since the 1970s.

No charges

Since the allegations, several TV networks have ended projects with Cosby and statues in his honour have been removed from public display.

 Cosby has not been charged with any sexual assaults. Because the alleged assaults happened years ago, he cannot be charged in most of the cases under US law.

A petition - sponsored by a sexual assault awareness group - has urged the White House to take back Cosby's medal.

The presidential award is given to people from all walks of life who have made exceptional contributions to society.

Previous honourees include Mother Teresa, Margaret Thatcher, Stephen Hawking, Walt Disney, Doris Day, Duke Ellington and Aretha Franklin.