Britney Spears supports gay marriage.

The 'Circus' singer - who passionately kissed Madonna on stage at the MTV Awards in 2003 - has vowed to fight for homosexual rights.

Writing on her Twitter page, Britney said: "Love is love! People should be able to do whatever makes them happy. I have lots of gay and lesbian friends and I want to see them get married.

"I'll do whatever it takes to make their dreams come true. Discrimination has no place in America."

Meanwhile, the 27-year-old pop star is currently struggling with the choreography in her current tour 'The Circus Starring Britney Spears'.

The dance routines are reportedly so demanding they make her vomit.

"She spins around for nearly five minutes some nights. The blood rushes to her head and when she gets down she complains of nausea and dizziness. There have been a couple of times when she ran off stage and vomited. She's asked if it can be changed."