Sylvester Stallone may come across as the ultimate guy's guy. But he says action stars like him are "the hardest characters to sell" to other men.

"Men are very competitive," Stallone said ahead of the world premiere of The Expendables 3.

"They go, 'Who's that? I'm sure he takes diuretic steroids, you know, he's shorter than he looks.'"

"It's very hard to do it. People think 'Oh it's really easy,'" said Stallone. "It's good to jump around but to get other men to like you, it's very difficult. Men are kind of stand-offish that way."

The third installment of The Expendables sees the team come into conflict with a ruthless arms dealer, played by Mel Gibson. Harrison Ford and Wesley Snipes join the cast of action legends.

And there's new blood, including Twilight heartthrob Kellan Lutz and mixed martial arts fighter Ronda Rousey.

The extended team of Expendables battle it out to bring down the bad guys and save the world.

The Expendables 3 opens in New Zealand on August 14.