The X Factor USA: Final Duet Partners Revealed
But unlike the UK version of the show, in which the judges sang with their own contestants, Demi will be performing with rival judge Simon Cowell's girl group Little Big Town, whileLeAnn Rimes - of whom she said: "I think she's amazing."
Cowell also took the chance to pay tribute to departing judge LA Reid.
"On a personal level, I'm going to miss LA Reid. On a business level, I'm also going to miss him," he said.
But when quizzed on whether Jon Bon Jovi could be a replacement, SiCo would only say: "Anything could happen, right?"
The show is screened on Wednesday and Thursday night by Fox in the US, with UK audiences able to catch it on Thursday and Friday night on ITV2.