Singer and actress Demi Lovato is to serve as the fourth member of the judges\' panel on the United States version of \"The X Factor,\" MTV.com said. The 19-year-old former star of Disney Channel\'s \"Sonny with a Chance\" is to join pop star Britney Spears, Simon Cowell and LA Reid as judges on Season 2 of the singing competition show next fall, the report said. Others considered for the job were Avril Lavigne, Janet Jackson and Mariah Carey, MTV.com said. Paula Abdul and Nicole Scherzinger were fired as judges after the first season of \"X Factor\" aired and wasn\'t a ratings winner. Their replacements -- Lovato and Spears - are expected to be officially announced this week. \"X Factor\" is based on a British series by the same name.