*FOX has finally confirmed a longstanding rumor about “American Idol,” while insiders at “The X Factor” are claiming that a long-unsubstantiated report about Mariah Carey’s involvement in the upcoming U.S. version is indeed true.

The network announced Wednesday what “Idol” producer Nigel Lythgoe teased to host Ryan Seacrest last week on his morning radio show: that Jennifer Lopez has inked a deal to return alongside fellow judges Randy Jackson and Steven Tyler for Season 11.

Seacrest tweeted the news just ahead of Fox’s official announcement: “We are back…On idol set in Savannah Ga with all the judges! Jen steven and randy..It’s like the first day off school!”

“Having both Jennifer and Steven return to Idol in 2012 alongside Randy is such a positive reflection on what was a wonderful and hugely successful season last year, and everyone is delighted,” Idol creator and executive producer Simon Fuller said in a statement announcing the news.

“Idol” will premiere its 11th season on Sunday, Jan. 22 at 8 p.m. immediately following the NFC Championship game on Fox.

On “The X Factor,” judges will have one superstar work in each panelists’ respective homes to whip their contestants into shape for the show. And Deadline.com is reporting that Simon Cowell is in final negotiations to have Mariah Carey as his personal pick to mentor his contestants from his house.

“He’s still finalizing her deal,” an insider tells the website.

Deadline’s Nikke Finke further reports…

The X Factor is pulling out all the stops to draw in other superstars as mentors. Contacts are being made now with “the Beyoncés, the Rihannas, all of them.” the insider tells me. The X Factor’s UK original series reportedly has signed up Usher as a mentor. Mariah’s name has been mentioned in connection with the U.S. show from the beginning but her twins pregnancy prevented her from being one of the judges. This is an interesting way for her and other music pros to be showcased. The result is that The X Factor could outglitz both ‘The Voice’ and ‘American Idol’ by combining the best elements from each.

The series will air Tuesday and Wednesday nights each week beginning Sept. 21.