Sylvester Stallone claims Dolph Lundgren almost killed him when they shot 'Rocky IV'.

The 72-year-old actor told his co-star to try and hit him as hard as he could when they got in the ring together - but he ended up in intensive care for several days after the 61-year-old Swede - who played Ivan Drago - ''almost stopped'' his heart with a punch.

He said: ''He hit me so hard he almost stopped my heart.

''I told him, 'Why don't we just do it? Just try to knock me out. Really cut loose as hard as you can.' That was a really stupid thing to say. Next thing I know, I'm on a low-altitude plane to the emergency room, and I'm in intensive care for four days. And there are all these nuns around.''

Stallone admitted one of the reasons why Dolph was cast in the film as his character Rocky Balboa's nemesis was because he ''hated'' him when they first met.

Speaking at the Cannes Film Festival, he said: ''Dolph Lundgren walked in, and I hated him immediately...

''I had to find a superhuman being as an opponent, someone who would be overwhelming.''

But the action legend admitted his hostility stemmed from the fact Dolph was ''literally perfect''.

Discussing how he reflected on why he disliked the actor, he said he realised: ''Oh, that's right, he's perfect ... This is what I would imagine they would create as an athlete -- someone who is literally perfect. Indestructible. Shoulders, calves, forearms, giant butt, neck, back, everything.''

Over the course of his career, the 'Rambo' star realised the key to his success is ''not to try and go outside my box.''

He added: ''Dustin Hoffman is not playing Rambo, and I'm not playing Tootsie.

''Every time [I went outside my box], I wound up in a 'Stop! Or My Mom Will Shoot'.''