As has been long rumored, Simon Cowell is leaving his judging spot on "American Idol" after his season to launch an American version of "The X Factor" on Fox.

The U.S. version of "X Factor" - which was responsible for the discovery of Leona Lewis in the U.K. - will debut in fall 2011. Cowell will serve as both executive producer and judge on the show, the format of which he created and launched in the U.K. in 2004.

The U.S. version will be produced by Syco Television and Fremantle Media North America. "X Factor" is currently shown in 17 countries.

"I'm thrilled that we have put a date on the launch of the U.S. version of 'The X Factor', and delighted to be continuing to work with Fox," Cowell said in a statement. "We have a fantastic relationship, a great team and are all very excited about this."

There was no immediate word on what Cowell's departure will mean for "American Idol," which debuts its ninth season tomorrow night.