Mark Ruffalo admits the ending for 'Avengers 4' remains undecided.

The 50-year-old actor plays the role of Hulk in the Marvel movies, but Mark has confessed that the reshoots of the much-anticipated movie will determine how the film concludes.

He shared: ''We don't even know what it's gonna be yet. We're not just doing reshoots. We're going to finish the movie, which we really didn't get to finish totally when we left it last year.''

In fact, Mark suggested that the directing duo - Anthony and Joe Russo - are currently uncertain as to how the movie will end.

He told The Marvelists podcast: ''I don't even know that [the Russos] really know exactly.

''Some of it is happening while we're there. It's pretty amazing. And we'll shoot some stuff and a few days later come back and reshoot it 'cause we wanna take it in another direction.

''It's a very living organism; even as we approach it being a locked picture, we're still working on it.''

Marvel Studios boss Kevin Feige previously promised that 'Avengers 4' will provide a definitive conclusion to the long-running narrative.

He said: '''Return Of The Jedi' was an ending for a long time and as a 10-year-old in 1983 that carried me through 30 years until there was a sequel.

''That hasn't happened before in the superhero genre. A new actor comes in and a new storyline starts right away. We wanted to do it this way because we think that the best stories have a definitive ending to a storyline.

''That's certainly what's going to happen next year with 'Avengers 4'.''