Simon Cowell, shown in February 2009, says he will leave American Idol at the end of the new season, which begins airing tomorrow. (Dan Steinberg/Associated Press)

American Idol judge Simon Cowell says he plans to leave the hit reality TV show after this season.

British-born Cowell plans to bring his The X Factor talent show to the Fox Network and says he will be involved with that show. The X Factor has been running six seasons in the U.K. and is franchised around the world.

Cowell is master of the nasty put-down and has been a fan favourite at American Idol, which begins airing its new season on Tuesday night.

Season 9 will be the first without Paula Abdul, who helped judge contestants for eight seasons, making the decision to leave the show in 2009 after being unable to reach an agreement on financial compensation with the producers.

Cowell announced his departure in Pasadena on Monday at a meeting of the Television Critics Association.

"I was offered a lot of money to stay on," he said. "But that wasn't the reason behind it. I wanted to do something different. I wanted a new challenge."

Fox executives did not say who might replace Cowell, but critics say it will be difficult to equal his caustic appeal. Talk show host Ellen DeGeneres is joining American Idol this season as a replacement for Abdul.

With files from The Associated Press