British musician Paul McCartney performs during his concert in Tel Aviv in this file photo from September 25, 2008.[Agencies]

LOS ANGELES- Former Beatle Paul McCartney and pop star Britney Spears are at the top of Simon Cowell's celebrity wish list as possible mentors on the upcoming season of "American Idol."

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," the British judge told reporters on a conference call on Wednesday.

Cowell said he would welcome the chance to see Spears on the show, which returns for its 8th season on January 13. The singer is on a comeback roll with a No.1 album and upcoming tour after almost two years of personal woes.

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

"American Idol" has produced some bonafide stars since its 2002 debut, including Grammy award winners Kelly Clarkson and Carrie Underwood.

Former contestants Jennifer Hudson and Jordin Sparks were both nominated earlier this month for Grammys.

"I absolutely love it when that happens," Cowell said. "There is so much snobbery in the music business about what we do on this show. So I think it is fantastic."