Rapper Nicki Minaj, country's Keith Urban pump up "American Idol"

LOS ANGELES (Reuters) - Rapper Nicki Minaj and country singer Keith Urban have signed up as judges for TV singing contest "American Idol," Fox television said on Sunday.

They will join Grammy-winning artist Mariah Carey for the 12th season of the show when it returns in January 2013.

Randy Jackson, the only remaining member of the original panel, will remain with the show, which lost some 20 percent of its audience last season.

The new judging line-up follows the departures earlier this year of Aerosmith frontman Steven Tyler and singer-actress Jennifer Lopez after two years. Carey's name was announced in July.

Minaj, 29, is the top female rapper in a hip-hop world dominated by male artists. She burst onto the music scene in 2010 and quickly made a name for herself with headline-grabbing outfits and multiple hit records including "Starships."

New Zealand-born Urban, 44, is married to Oscar-winning actress Nicole Kidman and is a four-time Grammy winner with sales of 15 million albums.

Producers had looked at several big names as possible additions to the panel, and rumored contenders over the past three months had included rapper Kanye West, pop star Katy Perry, Latin singer Enrique Iglesias and former "American Idol" runner-up Adam Lambert.

Minaj's and Urban's names were announced just hours before the first auditions for the new season in front of the judges in New York on Sunday.

"American Idol" creator Simon Fuller said in a statement that with the line-up of Carey, Urban and Minaj, "'American Idol's' star power has never been so great."

"American Idol" has been a ratings juggernaut since it debuted on Fox in 2002 but audiences are now only about half the more than 30 million who watched regularly in the show's 2005 and 2006 heyday.

The last season finale in May drew a! record low of just 21.5 million viewers and Idol lost its eight-year crown as the most-watched program on U.S. television to "Sunday Night Football."

Competition in the TV talent show market has increased dramatically in the last year with the hiring of pop star Britney Spears for "The X Factor" on Fox and radio DJ Howard Stern for NBC summer hit "America's Got Talent."

The NBC show "The Voice" boasts a celebrity judge panel of singers Christina Aguilera, Adam Levine, Cee Lo Green and country star Blake Shelton. It drew bigger audiences last week than the revamped "X Factor" contest.

Fox is a unit of News Corp and NBC is majority-owned by Comcast.

(Reporting By Jill Serjeant; Editing by David Brunnstrom)