Mila Kunis says Channing Tatum is her ''dream big brother''.

The 31-year-old actress stars opposite the 34-year-old hunk in new sci-fi adventure 'Jupiter Ascending' and she thinks the shoot would have been very difficult if they didn't get on so well.

she said: ''If we didn't like each other, this would have been a difficult movie for us both. We were attached to each other for seven months.

''Chan was so great to be around, very easy going, always in a good mood.

''He's like the big brother you dream about having. He's a guy's guy but also a very generous, warm and grounded human being... He also saved my life. I would have rammed myself straight into a camera if he hadn't grabbed me.''

Mila - who has four-month-old daughter Wyatt with fiance Ashton Kutcher - admitted the film was the most ''challenging'' work she had done because it required so much training and preparation.

She told Britain's HELLO! magazine: ''Physically, it was the most challenging role I've ever had.

''You train for six months and work out all day, five days a week. I've never been in better shape in my life and by the time we began shooting, I had zero body fat.

''I thought nothing would be harder than the preparation I did for 'Black Swan', where I lost 20lbs, but this was longer and more rigorous.''