Emily Blunt cried when she tried on her the 'Edge of Tomorrow' costume.

The 31-year-old actress and her co-star Tom Cruise had to don bulky plastic suits in the sci-fi movies, and though the 51-year-old actor - who tried his costume first - found the outfits heavy and uncomfortable he didn't want to tell the brunette beauty how ''challenging'' they were.

Speaking on US talk show 'The Tonight Show', he explained: ''When I got it [the costume] on I was like there was no way to make it any lighter ... It was plastic.

''But I didn't tell anyone because Blunt hadn't showed up. She'd trained for three months. I knew it was going to be challenging. It just looks cool on film, we gotta act in this stuff ...

''I never told her how heavy the suit was I made sure I was there the first day that she tried it on. She was doing her stunts.''

Asked about her reaction, he said: ''She cried.''

Tom wanted to make her laugh while she was in pain and in a stern voice he told her not to be a ''wuss'', which did the trick.

He added: ''I was standing there, I'm friends with her husband John [Krasinski]. Her first stunt in the film, I just looked at her, what do you say at that moment? I looked at her and thought I just have to make her laugh, so very seriously I said, 'Don't be such a wuss.'

''She stopped for a second looked at me and burst out laughing.''