Chris Pizzello, AP
The popular singer was approached by Cowell, who is notorious for his harsh critiques as a judge on 'American Idol,' to appear with him on his new show, but has opted instead to focus on her new role as a mother, as she is due to give birth to twins in April.
Carey would have joined longtime label head L.A. Reid, who announced his resignation from her label Island Def Jam last Thursday (March 17), to assume his new job as a judge on the Fox TV show which the former 'American Idol' star created in the U.K. in 2004.
Reid is credited with having been instrumental in Carey's 2005 comeback, and is rumored to have also taken a position at Sony Music, where the 'X Factor' winner will receive a recording contract. Reid's possible move to Sony has prompted rumors that Carey may do the same.
While Carey may not be on board, Cowell has boasted that the U.S. 'X Factor' will feature the best judging panel thus far, and will be revealed shortly. "It's gonna be a balance between guys and girls, and it should be a balance between people who have been singers and also, like me, have worked behind the scenes and know what they're talking about it," Cowell revealed. "It will be the best judging panel so far. I promise you: If I get the people I want, I'm really happy." Rumored judges include Taylor Momsen and Nicki Minaj.
Mariah Carey is expecting a twin boy and girl with husband Nick Cannon due in April.
Watch Mariah Carey's 'Touch My Body'