After a string of high-profile celebrities appearing on X Factor, Simon Cowell has announced who he would most like to have on American Idol.

Cowell wants to see former Beatle Paul McCartney and Britney Spears as possible mentors on the upcoming season.

But the chances of getting McCartney to appear on the most-watched American television show seem slim.

"We try every year to get Paul McCartney on but for whatever reason he won't come on," Cowell said.

The 49-year-old said he would welcome the chance to see Spears on the show, which returns for its eighth season next year.

"She would be first on the list. I would love to see her mentor the contestants. But if she doesn't want to do that and she wants to come on the show to perform, I would welcome her any time," Cowell said.

He said he would also like to see Beyonce on the show after her performance with Alexandra Burke on the X Factor final.

He also said he would welcome back singer-songwriter Lionel Richie and movie director Quentin Tarantino, who was a guest judge in 2004.

American Idol has produced stars including Kelly Clarkson, Carrie Underwood, Jennifer Hudson and Jordin Sparks.

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