Sharon Osbourne threatens to leave 'X-Factor'

After a 6-year hiatus, Sharon Osbourne was set to make a comeback to the judge's table at the U.K. "X-Factor," but she is reportedly suffering second thoughts.

Show creator Simon Cowell offered Osborne a $3 million deal to sit as head judge, but she has yet to sign the contract. According to the Daily Star, Osbourne's biggest concern is the health of her children. Kelly 28, recently suffered a seizure and Jack, 27, was diagnosed with multiple sclerosis last year.

"Simon is confident is is just a little wobble but he's not taking any chances after last year's disaster when Dannii Minogue pulled out just days before filming," said a source.

The source also said Osbourne is "lukewarm" over big changes to the show format.