Madonna says she was being deliberately "ironic" when she referred to President Barack Obama during her concert in Washington as a "black Muslim".
A video clip posted on YouTube by audience members at the Verizon Centre in the US capital captured the singer delivering a rousing, profanity-laced political speech about freedom.
In it the 54-year-old star said: "Now, it's so amazing and incredible to think that we have an African-American in the White House... we have a black Muslim in the White House... it means there is hope in this country, and Obama is fighting for gay rights, so support the man."
Mr Obama, who campaigning to be re-elected on November 6, is widely known to be a practicing Christian.
Responding to a media furor unleashed by the YouTube video, Madonna issued a statement through her spokeswoman saying her reference to Obama's religion was facetious.
"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?
"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.
Since Mr Obama's first presidential run in 2008, fringe groups and a smattering of opponents have espoused rumours that he is secretly a Muslim.
Similarly persistent, but unfounded, assertions by some political foes suggest that he was born not in Hawaii but outside the United States.
Madonna has been outspoken in her support of the president, going so far as to rip off her shirt during recent concerts to reveal the word "OBAMA" inked across her lower back.
During a concert tour in support of her latest studio album, MDNA, the singer has been grabbing headlines with a series of onstage antics.
At one of her Paris concerts in July, Madonna landed in hot water with France's far right National Front party after screening footage of party leader Marine Le Pen with a swastika superimposed on her face. The National Front said it would sue the star.
In August, Madonna spoke out at concerts in Russia in support of gay rights and the jailed members of the Russian punk rock band Pussy Riot.