50 Cent to quit if he doesn't beat Kanye

50 Cent has vowed to step down from music for good if he fails to sell more records than music rival Kanye West when both of their next albums go on sale on the same day.

The rapper, who will be releasing Curtis on September 11, the same day as West will be putting Graduation on shop shelves, sold 4.85 million copies of his last LP The Massacre.

West on the other hand sold 2.8 million copies of his last effort Late Registration, but now 50, real name Curtis Jackson, has challenged the 'Goldigger' hitmaker to a duel.

Jackson told the New York Daily News: "Let's raise the stakes. If Kanye West sells more records than 50 Cent on September 11, I'll no longer (perform) music. I'll write music and work with my other artists, but I won't put out any more solo albums.

"They would like to see Kanye West give me a problem because I've worked myself into a space where I've become the favourite. Everybody roots (for) the underdog when he goes against the favourite.

"And I bet this: When Kanye West's sales come in, he's gonna have a 70 per cent decrease cause Def Jam is gonna buy records (the first week) to keep him closer to 50 Cent. So watch the first week and then watch the second week. Watch his ass drop off the planet."

But he has admitted he doesn't mind if Kanye wins more awards than him, saying: "I didn't get one trophy for The Massacre. I don't get trophies, I get cheques. He gets the trophies. And I'll be sitting here like, 'It's cool 'cause I get the cheque.'"