Ashton Kutcher and Natalie Portman romp in new movie role

The pair star as best friends in No Strings Attached.

The romantic comedy charts what happens when they try - and fail - to keep sex out of their relationship.

Director Ivan Reitman, 64, has said of the flick, 'I noticed from my own kids that with this generation in particular, young people find it easier to have a sexual relationship than an emotional one.

'That is how the sexes deal with each other today.'

'I've done a lot of these kinds of movies, but this one is a little bit more grown-up,' Kutcher, 32, said.

'It looks at whether leaving feelings out of it actually works. For a new breed of woman, career comes first, and that has changed the nature of relationships.'

He told a USA Today, 'We should have just called the movie 'Clooney.'

'That's the kind of relationship George Clooney has had for the past 20 years. He seems happy.'

And the actor, who has been married to Demi Moore since 2005, said he was delighted to be working with Leon star Portman, 29.

'I've been trying to get her to do a movie with me about six or seven times. Every time I have a new one, I ask, 'What if we do it with Natalie Portman?'' he said.

The film is due to hit cinemas in the US in January 2011.