[Callum]

SIMON Cowell has lined up a string of superstars to perform at this week's live shows - as he tries to repeat X Factor's huge success.

We can reveal R&B legend Usher has been signed up for the final and singer Alicia Keys, and Hannah Montana star Miley Cyrus will also appear.

Brit acts will get in on the action too. Last year's winners Diversity will kick off the semi-finals tomorrow. And X-Factor boyband JLS will perform on Friday.

Cowell booked them after seeing the ratings boost of having stars such as Mariah Carey, Rihanna and Lady Gaga on X-Factor's live shows last year.

A show source said: "Simon saw how successfull it was on the X-Factor. So he decided to try it with BGT this year - and he expects a similar level of excitement. The US acts we have signed are huge stars, who sell out arenas around the world.

The source added: "We're excited to have some of the cream of world pop and British talent performing live.
"It promises to be a brilliant week - and we reckon this line-up will be a ratings smash."

Source: News of the World