Hilary Duff has a new fan in the form of John Cusack, after he was blown away by his young co-star’s performance in their new movie War, Inc.

Duff ditched her clean-cut image to play a trashy Middle Eastern pop singer in the Cusack-directed war satire, which also stars his sister Joan, Marisa Tomei and Sir Ben Kingsley.

And the actor/director admits he was shocked by her "wonderful" performance.

Cusack says, "We didn't know her. We knew she wanted to do the movie, which takes a lot of courage for a young girl who's already got huge fan base, who's a big pop star.

"I don't think any of us knew she would be quite as gifted, as intelligent as she is. Not only did she hold her, I think she's every bit as charismatic and wonderful as those other three actors."