A scheduling conflict forced Matt Damon to turn down the chance to be part of the most successful film ever made - he said no to Avatar.

The actor admits he was in talks with director James Cameron to take the lead in the 2009 sci-fi epic but there wasn't enough time for him to take on the project in between The Bourne Ultimatum and The Green Zone.

He reveals, "I talked to Cameron and I read the script and I knew the movie was gonna be a big hit. I really wanted to do Avatar and work with Jim Cameron and watch him direct and learn a lot.

"But we were finishing The Bourne Ultimatum and I couldn't leave; it was a scheduling issue."

Sam Worthington stepped in to replace the actor in the film.

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