Pop star Hilary Duff agreed to play a teen queen one more time when she realised John Cusack had written a part just for her.

The singer/actress, who has made a career from teeny bop TV and movie roles, was looking for a more mature film part when Cusack came calling.

Duff was working on her album Dignity last summer when Cusack called, asked her to dye her hair dark and consider one more teen role in his film War Inc.

She tells MTV News, "My agent called and was like, 'I got this script, John Cusack wrote it,' and I was like, 'Really? That's awesome, I love John.' But then he says, 'You'd have to play a pop star.'

"I was like, 'Oh no! I don't want to play a pop star. I don't want to sing (in a movie).'"

But, after reading Cusack's clever script and falling in love with her character, Yonica, Duff agreed to drop everything and get to work on the set.

And then Cusack called her direct: "He was like, 'You've got to go for it. I wrote this with you in mind.'

In the film, which was filmed late last year in Bulgaria, her pop star character gets caught up in an assassin's scheme in a fictional Middle Eastern country.