'AMERICAN IDOL' JLo WILL Return Asked to Replace Mariah

Jennifer Lopez has been approached by Fox execs to return to "American Idol" for the balance of the season ... to replace Mariah Carey ... sources connected with the network confirm to TMZ.

We've learned Lopez will appear on the now ratings-challenged show on May 16 to debut her new single, but Fox has bigger ideas -- they want to stop the hemorrhaging quickly and bring the former judge back on the show.  The Hollywood Reporter first posted the story that JLo could be returning.

And the show is in trouble.  Last week's ratings were the worst since the show debuted in 2002.

Sources tell us Fox is scrambling to find a solution, and ironically they think Lopez could be the answer.  We say ironically because network execs would not ante up the cash JLo wanted to stay on the show this season.  

We're told as of now ... no deal has been made.

UPDATE:  A Fox spokesperson tells TMZ ... "This is just another ridiculous "Idol" judge rumor, likely started by talks of Jennifer performing on the finale."