Ellen DeGeneres is known for being nice. But the new "American Idol" judge said that she's ready to be honest with the show's contestants, good or bad.

"I think it's going to be hard, but as my career has grown. ... I've learned how to be tougher and learned how to say no," DeGeneres said Thursday, a day after her addition to the show was announced. "I think I can do it and I think I can do it in a respectful way."

Any bluntness will be reserved for fellow judge Simon Cowell, known for his barbed remarks to contestants and colleagues.

"When Simon is rude and mean, I will tell him he's rude and mean, just like I tell him when he's on my show that he's rude and mean," DeGeneres said, referring to "The Ellen DeGeneres Show."

She'll continue with her daytime talkfest as she takes on "Idol" judging duties for the show's ninth season, starting in January.

DeGeneres, who signed a five-year deal with the top-rated Fox singing contest, said she was "shocked and excited" when the opportunity came her way.

The fourth seat opened up when Paula Abdul resigned by way of Twitter in the midst of a contract dispute this summer. DeGeneres, who hasn't been part of the parade of guest judges taking Abdul's place in preseason auditions, came to the attention of "American Idol" producers another way.

After serving as a guest judge on Fox's "So You Think You Can Dance," the network and "Idol" creator Simon Fuller "started sniffing around and said, `Are you interested?' and I said, `Yes, of course. ... I love that show and I'd love to do it.'"

In online postings, some "Idol" fans have applauded the comedian's selection for the humor she'll bring to the show. Others, however, have questioned her credentials.

Cowell, Randy Jackson and Kara DioGuardi all bring deep record industry experience to their critiques.

"I know as much as anybody who goes out there and buys a record. I know what I like and I think I do know what is special and has the `it' factor," DeGeneres said in response, adding that she's brought talented new artists to public attention on her talk show.

She hesitated to name her one favorite "Idol" contestant from years past, instead listing Kelly Clarkson, Chris Daughtry, Adam Lambert, Carrie Underwood and Kellie Pickler.

But DeGeneres has a ready answer when asked if she and DioGuardi, who appeared onstage last season in a swimsuit with a contestant dubbed "Bikini Girl," might get into a similar duel.

"That I can guarantee you will never happen. I don't ever, ever like to definitely answer anything with a yes or no, but that's a no," she said firmly.