Demi Lovato has a ''bold, strong personality''.

The feisty US 'X Factor' judge has already clashed with the show's creative director Brian Friedman over her contestants' performances and Brian admitted their relationship has been tense as a result.

Speaking at the 'X Factor' finalists party in Los Angeles on Monday (05.11.12), he exclusively told BANG Showbiz: ''It's definitely been a new experience in trying to build new relationships and getting to know each other. Demi and I are a learning process because we are brand new and she is a bold strong personality.

''We definitely have contrasting ideas so it's been tough but I think we are getting there. We had a chat and decided to work together and make sure that we're not giving conflicting ideas to her contestants. I think when we go get there her category is really going to thrive.''

Brian has found it easier to collaborate with Britney Spears and Simon Cowell as he has a good relationship with both judges having worked with them in the past.

He added: ''Simon and I have had seven years to work this out and my relationship with Britney is incredible. She trusts me when it comes to staging and choreography. ''

Brian also revealed he would love if Britney and Demi performed a duet at one of the live shows and would jump at the chance to choreograph it.

He said: ''A Britney and Demi duet would be so amazing, I am going to have to talk to them about that.''

'The X Factor: USA' airs on ITV2 Thursday (08.11.12) from 8 - 10pm.