Katy Perry will pick new US Idol

Katy Perry has been signed up as a guest judge on American Idol.

Executives at TV channel Fox have asked the I Kissed A Girl singer to appear to help replace Paula Abdul, who left this week.

Guest judge: Katy Perry

Perry, 24, joins Victoria Beckham, 35, as one of the guests who will occupy the fourth chair alongside the resident judges — music mogul Simon Cowell, producer Randy Jackson and songwriter Kara DioGuardi.

But Fox chairman of entertainment Peter Rice said neither Perry nor Beckham was "necessarily being considered for a permanent judging role".

On Australian Idol, former Westlife star Brian McFadden, who now lives Down Under, has been tipped to replace judge Kyle Sandilands, in trouble over a radio interview.