AceShowbiz - Matt Damon is still wrestling with his decision not to accept a role in one of the highest grossing films of all time, "Avatar".

The Oscar winner reveals he was approached by "Titanic" filmmaker James Cameron and asked to appear in the 2009 blockbuster, but he said no.

Damon was also offered a 10 ten per cent cut of the film's gross, which would have netted him roughly $250 million (£200 million).

"Jim Cameron offered me 'Avatar'," Matt tells GQ. "And when he offered it to me, he goes, 'Now, listen. I don't need anybody. I don't need a name for this, a named actor. If you don't take this, I'm gonna find an unknown actor and give it to him, because the movie doesn't really need you. But if you take the part, I'll give you 10 per cent of (profits)."

"I told (pal) John Krasinski this story when we were writing 'Promised Land'... and he goes, 'If you had done that movie, nothing in your life would be different. Nothing in your life would be different at all. Except that, right now, we would be having this conversation in space.' "

"I've left more money on the table than any actor actually."

Damon shares he chose to stick to his commitment with "The Bourne Identity" franchise instead of shooting "Avatar", and still regrets not having the chance to collaborate with the iconic director.

"It would have caused a problem for Paul Greengrass and for all my friends on 'The Bourne Ultimatum', so I couldn't do it," he adds. "Cameron said to me..., 'Well, you know, I've only made six movies'. I didn't realise that. He works so infrequently, but his movies, you know all of them. So it feels like he's made more than he has. I realised, in having to say no, that I was probably passing on the chance to ever work with him. So that sucked and that's still brutal. But my kids are all eating. I'm doing OK."

The lead role in the fantasy epic ultimately went to Australian actor Sam Worthington.