Cee Lo Green thinks US 'X Factor' bosses should be "concerned" about 'The Voice'.

The 'Bright Lights Bigger City' hitmaker - who sits alongside Adam Levine, Christina Aguilera and Blake Shelton on the panel of the NBC talent show - isn't worried about the rival singing programme going up against the series because he believes they are "completely different".

Speaking on 'The Tonight Show', he said: "The premises of each show are just completely different. I think if anybody should be concerned, it's them."

Earlier in the current series of 'The Voice', the 37-year-old singer broke down in tears three times in an episode of the talent show during the emotional Battle round.

Cee Lo was crushed while struggling to choose who to send through to the next round out of hopefuls Justin Hopkins and Tony Vincent, and he was also cried during rehearsal when one wannabe sang Cindy Lauper's 'True Colours'.

Following the performance, he said: "This song moves people, that's what this song is doing right here.

"That song made me cry, man. I'm proud of you all, man. Wow, dude. OK man, OK I surrender.

"I don't sing like that. I can't help but be humbled by it. Final words of advice, live it, love it and just be in the moment."