Marion Cotillard says her sex scene with Brad Pitt was "awkward".

Marion Cotillard

Marion Cotillard

The 41-year-old actress enjoys an on-screen romance with the 52-year-old hunk in their new movie 'Allied' but has revealed that one particularly steamy scene - in which their characters get acquainted in the back of a car during a sandstorm - left the pair in fits of laughter because it was "so weird" to have every step planned out for them.

Speaking at a press conference for the movie over the weekend, the star said: "We rehearse and had a very determined choreography, and then it allows you freedom.

"When you know exactly what your body will do, then you can act and you can be free to give the emotions and give the feelings because you won't think, 'What am I going to do next? Am I going to go on top of him?' It's an awkward situation.

"We laughed because you need to get it out because this is so weird. And so you get this time of looking at each other and saying, 'OK, this is so weird.' And then we go into this and then I'm going on top of you and then we are going to kiss."

The actress even had to teach Brad how to speak French for the role, as 'Allied' tells the story of a Canadian intelligence officer (Pitt) meeting a French Resistance fighter (Cotillard) during World War II.

She added: "He had this commitment to [learn French] the best he could, which was really, really impressive, so I helped him by being very tough.

"I was very honest with him. But at the same time, I really wanted to support him in this process that I went through, and I know how hard it is."

And Marion - who was previously forced to deny affair allegations in the wake of Brad's split from estranged wife Angelina Jolie - recently described her co-star as "a good man".

She said: "[Brad is] such a good man. Of course he's an amazing actor. He's such a good person that it's really not difficult to get along with him."