Pop icon Madonna has reportedly been booked to appear on the final of "The X Factor".

The 56-year-old has been urged by its creator Simon Cowell to appear on the last show in the current series in a bid to boost flagging ratings, but a source says she will only do so if she has a significant degree of creative control over her own performance.

"Madonna will have been provisionally booked because the final can be subject to change if an artist doesn't approve of the finalists - especially if they have agreed to sing with them," dailymail.co.uk quoted a source as saying.

"Someone like Madonna will want a lot of creative control over her appearance, but for Simon the ratings will be worth it," added the source.

But the source added that there were also conditions Madonna must agree to.

"She has been told that her label will be expected to pay for any stage props and backing dancers she brings with her," said the source.

And Madonna's appearance could also boost sales of her as-yet untitled 13th studio album, due for release just after the live final.

Meanwhile, another source said: "It had been rumoured that Irish rockers U2 were being lined up to take part. But that has not happened and the confusion may have come because they share the same manager Guy Oseary".