Britney Spears and former Disney Channel star Demi Lovato will join talent show “The X Factor” as judges when the U.S. version of the contest returns to television in September, Fox television and the show's creator Simon Cowell said on Monday. Cowell said in a Twitter message that Spears, 30, the world's biggest pop phenomenon of the 2000s, will join him on “X Factor,” which searches for a new pop star from tens of thousands of ordinary Americans. Spears will be joined by singer and actress Lovato, 19, to fill the judge's seats left by Paula Abdul and Nicole Scherzinger, who were both fired by Cowell after a disappointing first season in 2011. Cowell announced the news on Twitter, sending a photo of himself with record producer Antonio “L.A.” Reid, Spears and Lovato and saying “Can't believe it's finally happening. Very exciting!” His Tweet landed moments before Fox made the official announcement in New York in a presentation to advertisers of its new 2012-13 season programming.