Fox has announced that tonight's episode of The X Factor -- the first live installment of the series -- will find the judges eliminating five contestants.

The surprise announcement means the contestant pool will be whittled down to 12 by the end of the episode.

The show, which has so far failed to earn the kind of ratings -- 20 million viewers -- that judge Simon Cowell said he would consider a success, will air an extended two-and-a-half hour episode for its first live showing.

The remaining 17 acts will perform after having worked with stylists, vocal producers and choreographers.