The man behind the successful Rambo and Rocky franchises has also brought Jason Statham, Jet Li, Mickey Rourke and Dolph Lundgren on board for the story of a team of mercenaries who head to South America on a mission to overthrow a dictator.
"Arnold, Bruce and I will be working together for the first time, maybe in two weeks, so I had to grow back my beard and get ready to film it in Los Angeles," Stallone told reporters at the Venice film festival where he is receiving a special award.
"It's very difficult to get us all together at the same time. It's impossible to get all those egos in the same room," the 63-year-old joked.
He said The Expendables would seek to put some of the punch back into action movies in an era when computer generated effects are increasingly dominating the genre.
"I wanted to do a film that was more about men and just doing things that we did back in the '80s and '90s with films that were a little bit more men on men, and actual physical stunts and also a story that isn't super-gigantic.
"And the thing was to find certain personalities that never would ever work together normally and put them altogether. It's like a dream team."
He also spoke about his next Rambo venture, the fifth in the series, which will enter the realms of science and technology.
"I don't want to keep repeating myself and just doing films about war," said Stallone. "This is a very psychological film about sophisticated man fighting primitive man.
"It's actually possible today, with all the cloning and stem cell research, to actually have some experiments that don't work very well and get out of control."
Stallone, best known as an actor but who is also a successful screen writer, said he wanted to direct more.
"What's very unusual in my life is that I'm now, at this age, starting to develop what I should have done 20 years ago which is more directing and writing and especially not the movies I am in.
"The key will be to direct other people and write for other people. Then that cycle will be broken."
The action star also predicted a swing in Hollywood away from big-budget blockbusters and toward smaller, independent film making like that championed in the 1970s by the Martin Scorsese, Francis Ford Coppola and Brian De Palma.
"You have films that cost $200-300 million and when they don't work the entire studio is gone, a thousand people lose their jobs. The volcano is ready to explode.
"The day of independent cinema is coming back. I think the young people in the audience are going to demand it. 'Okay, we've seen enough fantasy, we've seen enough big spectacle, what about stories about us?'"
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