The No Doubt star reveals she went on "a bunch of auditions" for the role of assassin Jane Smith in the action thriller, and feels she "almost got it".
However, she is unsure if she would have signed on for the part had she known she would be cast opposite Brad Pitt, who portrayed rival contract killer John Smith.
"(It was) very competitive and I wanted to do it, but I wanted to do music more," she tells U.S. radio host Howard Stern.
Gwen previously discussed her audition in a 2008 interview with Vogue magazine, revealing she was thrilled she was being considered alongside Hollywood superstar Angelina.
"It was between me and Angelina Jolie, and I'm like, 'Oh, great. I got a shot here'," she told the fashion magazine at the time. "The whole acting thing really feels like something I could do. Whenever I've done it, whenever I had moments where it works, it's just like performing. You hit a moment. And that's what movies are: a series of moments."
Angelina and Brad famously debuted as a couple following the premiere of the movie and in the midst of his separation from actress Jennifer Aniston. Brad and Jen went on to divorce in October, 2005 and Pitt and Jolie, who now have six children together, wed in 2014.
"It took until, really, the end of the shoot for us, I think, to realise that it might mean something more than we'd earlier allowed ourselves to believe," Angelina told Vogue in 2007 of their evolving relationship. "And both knowing that the reality of that was a big thing, something that was going to take a lot of serious consideration."
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