Madonna insists she was being "ironic" when she referred to US President Barack Obama as a "black Muslim".

The Queen of Pop made the remark while performing in Washington on Monday. In between songs, she urged the audience to support Obama during the on-going presidency race as it is so "amazing and incredible" that America has a "black Muslim in the White House".

The president is open about his Christian faith, so there was widespread shock about Madonna's claim. She has responded via her spokeswoman.

"I was being ironic on stage. Yes, I know Obama is not a Muslim - though I know that plenty of people in this country think he is. And what if he were?" she said.

Since he assumed office in 2009, Obama has been beset by rumours about his birth place and religion. It was claimed he was born outside America where he was actually welcomed into the world in Hawaii and was Muslim.

Madonna claims people have ignored what she was actually trying to say.

"The point I was making is that a good man is a good man, no matter who he prays to. I don't care what religion Obama is - nor should anyone else in America," she said.