Pop star Beyonce Knowles was desperate to land the lead role of Effie in Dreamgirls, but was forced to take a smaller part because the director wasn't convinced she could act.

Despite appearances in comedies Goldmember and The Pink Panther, Knowles couldn't convince director Bill Condon she would be able to tackle the dramatic role--which eventually went to Jennifer Hudson.

Knowles insists she was happy to take the smaller part to prove her talent as an actress, saying, "I'm already a star. I already have nine Grammys. Everyone knows I can sing.

"I did this because I wanted people to know that I can act and I can play someone so different from myself."

The ¡°Irreplaceable¡± singer admits she would have loved to have sung Effie's show-stopping number ¡°And I Am Telling You I'm Not Going,¡± and would have gladly gained weight for the role.

Instead she lost weight to play Deena in the movie.

She explains, "I wish I could have gained 20 pounds and played Effie. I absolutely would have, but Bill didn't even believe that I could be Deena. So imagine if I would've said, 'Bill, I want to be Effie.'

But Knowles has high praise for her costar's performance, adding, "Jennifer Hudson had such pressure. First of all, never being in a film and never having done an album and still having to live up to those expectations, she did incredible."