US 'x factor' bosses may shun Cheryl Cole for a homegrown star.

The singer has been tipped to join Simon Cowell on the judging panel of the pop star search show when it heads Stateside after impressing on the UK version, but producers are unconvinced and believe American audiences may prefer a more recognisable star such as Rihanna or Katy Perry.

A friend of Cheryl's rumoured boyfriend Derek Hough said: "Everyone thinks Cheryl has the judging job on US 'X Factor' in the bag.

"The truth is, nothing has been signed and The Producers still aren't convinced.

"They are more keen to get a big US star like Katy or Rihanna on the panel - someone who will bring credibility to the show and who is already popular in the US."

Simon is now reportedly doing all he can to convince his American business partners that the 27-year-old Girls Aloud star has what it takes to draw audiences in across the Atlantic.

The source added to The Sun newspaper: "Simon has been the only one pushing for her and trying to convince everyone that she'll be a big hit.

"They want to see if the American public warm to her before she takes on such a high-profile role in one of the biggest shows on US TV.

"There have been lots of heated conversations and debates about it."

The possible change of plan would come as a big blow to the brunette beauty - who earlier this month was reported to be spending $3.5 million on a property in California so she can be near the TV studios where the US 'X Factor' will be filmed.