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Singer Katy Perry is to stand in as an American Idol judge. ((Stephen Lovekin/Getty Images))

Singer Katy Perry and former Spice Girl Victoria Beckham will fill in as guest judges during the auditions for American Idol this season.

Fox executives announced their roles in Los Angeles on Thursday, just a day after Paula Abdul said she was leaving the popular reality TV show.

Perry and Beckham are among the personalities Fox will use to fill the fourth judge's chair on American Idol.

"We were hoping Paula came back," Fox chairman of entertainment Peter Rice said. "We love Paula. She's been clearly wonderful on the show for eight years and was an important part of the Idol family."

But he held out little hope that Abdul would change her mind. She apparently announced her resignation on Twitter.

" We have to look at it as an opportunity for the show to bring a different energy to it and an energy that can be entertaining for the public," Rice said.

Beckham, who was known as Posh Spice, and Perry, who had a hit with the song I Kissed a Girl, will judge American Idol auditions beginning Aug. 9.

They are not necessarily being considered for a permanent judging role, Rice said.

"What we need to find is someone who has great chemistry. It really is a casting job. Our job in the next four or five months is to consider what makes this the most fun, the most entertaining show," Rice said.

Idol producers renewed the contract this week of songwriter Kara DioGuardi, who was added to the judging panel this season. Simon Cowell, Randy Jackson and host Ryan Seacrest also are under contract.