Simon Cowell

Simon Cowell says that NBC is being "cold-hearted" by adding another night of The Voice, which will now go up against Fox's X Factor.

"This is a cynical, cold-hearted, unprofessional way of doing business," Cowell told TMZ. "These guys have really got it in for us. It's nothing short of dirty tricks."

The Voice premiere expands to three nights to battle The X Factor

Cowell added that he was under the impression the two networks had a "gentleman's agreement" where The Voice would air on Mondays and Tuesdays and X Factor on Wednesdays and Thursdays. This week, NBC announced that a third night of The Voice will air on Wednesday, Sept. 12 at 8/7c, the same time that X Factor will premiere. Cowell says the schedule shift was made out of fear.

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"The reason they've done this is they don't want people to see X Factor because they've heard how good the series is," he said. "They don't want their audience to see Britney Spears. They don't want their audience to see Demi Lovato. ... Britney is not going to appreciate the fact that Christina [Aguilera]-- who has been a bit of a rival -- isn't allowing Britney to have a night of her own. She's going to be devastated because she's put her heart and soul into this."

However, Mark Burnett, who produces The Voice, shoots down Cowell's claims. "There was never ever a meeting or a discussion of what my show was up against," he told TMZ. "The fact is ... it shows you where our minds are at and where others are because it literally never crossed my mind. I'm just glad we're on Simon's mind."

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