Ben Affleck thinks Matt Damon is "very bitter" about not being Batman.

Ben Affleck and Matt Damon

Ben Affleck and Matt Damon

The 44-year-old actor has taken on the responsibility of directing, producing and portraying the much-loved caped crusader, but Ben has joked that his 'Good Will Hunting' co-star and long-time friend is a little bit jealous.

He shared: "He's very bitter. All he gets to do is 'Jason Bourne'. Just keeps doing it again and again. We get it."

Ben said Matt shouldn't be too jealous, because his Oscar-winning friend has also enjoyed his own success.

Ben said: "He's had his share. I got we 'Bought a Zoo' on a loop in the house."

The Batman actor also opened up about his well-known friendship with Matt, who has been a close pal of his since they were young.

Ben admitted it has been incredible for them to emerge as two of the biggest stars on the Hollywood scene and yet they still maintain a close bond.

He told ABC News: "Being friends and having a guy to go through all that stuff with.

"To have a relationship and have a sense of humour about it, it's crucial."

This comes shortly after Ben - who has kids Violet, 11, Seraphina, seven, and Samuel, four with estranged wife Jennifer Garner - revealed he will spend Christmas with Matt.

He shared: "I can tell you that we're going to do skiing in Montana with our family and Matt Damon's family and my brother's family.

"It should be a lot of fun."

And prior to that, Ben joked about how he keeps his friendship with Matt "fresh".

He quipped: "You know Matt [Damon] and I, we just we have good sex. That's what keeps it fresh."