Arnold Schwarzenegger thinks he tried "too hard" to work alongside Sylvester Stallone in the past.

The Terminator star and the Rocky actor - who teamed up for action movie The Expendables in 2010 - are reuniting for forthcoming action-thriller The Tomb, and Arnold believes it is now an ideal time to collaborate with Sylvester.

"We worked really well together. The funny thing is we have tried, I think, our entire careers to always work together. We have talked about it for three decades and it never happened. I think we tried maybe too hard ... But now after the governorship, somehow this just fell into place," the 64 year-old former Governor of California said.

Sylvester admits the pair were "competitive" when they started their respective acting careers, but they have both now realized that teaming up with one another is beneficial: "We're just a couple of old war horses talking about the oddest subjects on the planet. I think in the beginning we were competitive - there's no question about it. A little alpha territorial. And then we realized it was good for our careers [to work together]."