Simon Cowell thinks Khloe Kardashian is the perfect 'X Factor' USA host because she is "unpredictable".

The reality TV judge said he hopes the 28-year-old 'Keeping Up With The Kardashians' star continues to express her outspoken attitude and opinions alongside her co-host Mario Lopez on the show which began it's live stages last night (31.10.12).

The 53-year-old told USMagazine.com: "I like that -- [the hosts] are there to have opinions, and I think that's what was lacking last season. It's important that [they] are allowed to pitch in. If they disagree with the judges, they're entitled to say something!"

Simon said he thinks Khloe is eager to prove she is more than just another reality TV star and believes she is up for the challenge.

He said: "I think she wants to prove [to] anyone who doubted her that she's capable of doing the job. I don't know her well, but...she really has got a fun personality. I think she gets what her role is -- she's there to be a voice for the contestants and to have fun with it.

"On live TV, things do go wrong...I kind of like to see the unpredictable, and I quite like to see people under pressure just to see how they deal with it. You don't want robots, you want human beings.

"When you want to go off script, go off script. That's more fun than someone just reading on a teleprompter."

Meanwhile Simon also praised his fellow judge Britney Spears - who admitted she was "very nervous" ahead of the first live show last night - and said she has impressed him with her skills.

"[Britney has] been a lot better than everybody thought, She's very engaged...She has been, I think, a very, very good judge."