BY LARRY CARROLL | On June 14th, Matt Damon is Jason Bourne. At least, that's what the billboards say, and after watching him take apart one guy after another in the film, I doubt anybody would argue the point with him. Bourne, the protagonist in three best-selling books penned by the late Robert Ludlum, is a confused CIA assassin who is trying to stay alive long enough to find out who he really is. It's a role that involves a great deal of physicality, which is fine by Damon.

"I had about three months to work on the martial arts, boxing and weapons training, which was like summer school for assassins," jokes the star. Dressed in a t-shirt and jeans, he looks much younger (and less deadly) then he does on screen. "The fighting is a lot of fun, and although it's meant to look violent, no one gets hurt. You make it look as real as possible, but at the end of the day it's choreographed like a dance. Then you put the intent in, and it all cuts together. Nick Powell (the stunt coordinator on the film) is really great at choreographing these fights. He did Braveheart and Gladiator, which had really compelling battle and fight sequences."

In one of the most memorable scenes of the movie, Damon's Bourne goes tete a tete with an assassin using the Filipino martial arts discipline of Kali. While battling with the other actor, who was much larger than Damon, the two were encouraged to come as close as possible with their air punches. Sometimes, things got a little too realistic. "He did hit me once, pretty hard," Damon grimaces. Damon also had a tendency to accidentally land the occasional punch, "But I'm sure it hurt me a lot more then all the times I ever hit him."

Damon got physical in the past in films like Courage Under Fire and Saving Private Ryan, and proudly declares that he did most of his own stunts in the film. But these stunts involved more than just running and shooting, especially the thrilling sequence in which he must scale a wall. "Climbing down the face of that building is probably the most grueling thing I've had to do," the actors recalls. "I'm not what you'd call an experienced rock climber."

Reflecting on the choice of this role, he speaks highly of his director, indie film auteur Doug Liman (Swingers, Go). "I wanted to do The Bourne Identity because of Doug and his sensibility. I knew that he would not make a standard Hollywood action movie, and I knew that if I was ever going to try something like this, I'd want to do it with a guy like him."

Damon enjoyed Liman's hands-on technique with the lensing of the film. "The directors I've really loved working with are the ones who are right in there, watching it unfold live. Someone like Doug, who's usually operating, doesn't miss anything. He's framing it, he knows what's in and what isn't, and what's captured and what isn't."

One of the unique decisions that Liman made was in the casting of Bourne's love interest. He insisted upon the role going to Franka Potente, the star of arthouse films Run Lola Run and The Princess and the Warrior.

"Casting Franka was a great idea," Damon declares, "especially since the story takes place in Europe. Having this incredible German actress added an entirely different dynamic of culture and language to the story." Potente brought out the best in Damon, who was impressed with her acting style. "She made some great choices," he remembers. "For instance in the apartment scene, as written, after the guy goes jumping out the window, which is bizarre, she was supposed to react and start screaming. Instead, she acted like she was in shock, and said, 'Why did that guy go jumping out the window?' I think that was a really cool acting kind of moment. A really great choice and a really imaginative choice on her part. She made the movie a lot better by bringing in stuff like that."

It's been five years now since Damon and his best friend, Ben Affleck, burst onto the scene and won an Oscar for Good Will Hunting. Now, he and his friend have competing action films at the box office, Damon with Bourne and Affleck with The Sum of All Fears. Questioned about whether audiences will enjoy the two as action heroes, Damon says, "I think so. These movies are different, and I think they're always ready for something that's a little different."

So, I asked him, who would win in a fight between Affleck's character of Jack Ryan and Jason Bourne? "Bourne would kill him," Damon laughs, flashing that patented smile. "Ryan's an analyst, he'd go down no problem."

Then Damon pauses briefly and thinks about the film that Affleck is currently shooting. "Well, he is Daredevil (the comic book character) next. Now that would be a good fight."