The rivalry for top TV singing contest has increased yet another notch, as NBC's The Voice added hit R&B singer Usher and Latin pop star Shakira to its lineup.

Late Monday, NBC revealed the two new additions would step in next spring while original "coaches" Christina Aguilera and Cee Lo Green take a break to pursue other projects.

Aguilera is heading out on tour to promote her upcoming album, while Green is working on new music and developing an NBC sitcom based on his life.

"As I have expressed since Day One of the show ... I am a singer and performer first and I am so excited to get back to that love," Aguilera said in a statement.

Colombian singer Shakira, seen performing in Germany, will join Usher as new coaches on The Voice next spring, when Christina Aguilera and Cee Lo Green take a break from the show. Colombian singer Shakira, seen performing in Germany, will join Usher as new coaches on The Voice next spring, when Christina Aguilera and Cee Lo Green take a break from the show. (Fabian Bimmer/Associated Press)

She and Green noted that they are eager to return to The Voice in future seasons. Fellow singers Adam Levine and Blake Shelton will remain on board.

The show, which has chart-topping artists choose and then coach talented amateur singers, started out as a mid-season replacement but earned solid ratings and a strong audience. It moved to a fall start and kicked off its third season last week.

The Voice announcement came the same day Mariah Carey and her new fellow American Idol judges, country star Keith Urban and rapper Nicki Minaj, spoke to media in New York.

Fox's American Idol, which has been the ratings leading among TV singing competitions, has nonetheless seen its viewership erode in recent years.

Though it got a boost when pop star Jennifer Lopez and Aerosmith rocker Steven Tyler joined its judging panel in 2010, the show was forced to enlist new judges when the pair announced their exit in July.

Fox also produces the rival singing contest X Factor, an American version of the British show. Created by original American Idol judge Simon Cowell, X Factor introduced pop singers Britney Spears and Demi Lovato as judges for its most recent edition.

With files from The Associated Press