Chris Cooper’s got pedigree. The 56-year-old American actor began his impressive big screen career with the great independent filmmaker John Sayles, making four films with him, including Cooper’s 1987 debut, the miner’s union drama Matewan, and the excellent Tex-Mex murder mystery Lone Star. Hollywood called soon after, offering Cooper plumb parts in studio movies such as American Beauty, in which he played a closet homosexual military man, and the Jason Bourne trilogy, in which he takes the role of Matt Damon’s CIA nemesis. An Oscar win for his supporting role as the eccentric orchid thief John Laroche in Adaptation cemented Cooper’s reputation as a guy with the easy screen presence of his yesteryear namesake, Gary, but also marked him out as a formidable actor with great range.

Cooper’s new film, Breach, represents his first leading role in a prestige studio picture. It recounts the true story of the treasonous FBI agent Robert Hanssen who, for 22 years, sold secrets to the Soviets, making him responsible for the worst intelligence leak in American espionage history before he was apprehended in 2001. For Cooper, who’s coming to the Edinburgh International Film Festival for the gala premiere of Breach and an ‘In Person’ masterclass session, the particular challenge – and peculiar pleasure – of playing the political reactionary, religious conservative and deeply contradictory Hanssen arose from how very unlike him the character is.

‘It’s part of the enjoyment and the challenge to take a completely different stance on life,’ Cooper says in the measured midwestern drawl that’s stayed with him since his formative years growing up in Missouri, ‘to embrace another character’s politics and religious values.

‘But oh no,’ he laughs, ‘I couldn’t relate to his political views at all. There’s very little I can connect personally to Hanssen, other than extreme shyness as a young person, adoring his wife, and being secretive – I consider myself a rather solitary person.’

Cooper was raised on a cattle ranch outside of Kansas City (where he was born), and worked with his father and older brother as a blue-collar cowpoke. ‘That was a very attractive life when I was younger,’ Cooper says. ‘It was very physical, and I considered very that seriously as a life’s work. But I always had the theatre in the back of my mind. When I was 16 or 17 I started breaking away from my friends who were getting into a bit of petty crime I didn’t want to be part of, so I offered my time at a local theatre in Kansas City, doing anything, sweeping the floors, scene shifting. It was a great education to watch these actors every night. My interest in acting started there.’

Cooper studied drama at the University of Missouri, did a couple of years of summer stock, and then moved to New York City, where he had a ball acting on stage for 12 years. In 1983 he married the actress Marianne Leone (best known here as Joanne Moltisanti in The Sopranos), who pushed Cooper into making films and kick-started his fruitful working relationship and close friendship with Sayles. In 1987 Cooper and Leone had a son, Jesse, who was born with cerebral palsy, who died from causes related to the disease two years ago, aged just 17. Jesse’s parents, who now live in Kingston, Massachusetts, set up the Jesse Cooper Foundation and work tirelessly as advocates for children with special needs (to that end Cooper and Leone are currently collaborating on a film about a mother’s relationship with her severely disabled daughter, Hurricane Mary).

From this background sketch you’ll perhaps have gleaned that Cooper, who speaks like a cowboy, conducts himself with the courtesy of a gentleman rancher, and has experienced something of the bohemian life as well as great personal loss, is a world away from the deceitful but otherwise straight-laced FBI man Robert Hanssen. Cooper describes his own politics as ‘left of left’. Sayles, who most recently cast him as a dimwitted politician and thinly-disguised pre-White House George Bush in the political satire Silver City, calls him a news junkie.

‘As soon as I wake up,’ Cooper confirms, ‘I listen to National Public Radio for the early coverage of what’s happening that day, and I’ll take a look at CNN throughout the day. That really kicked in after 9/11.’

Cooper talks confidently and freely about politics and current affairs: ‘I feel pretty confident we’ll get a Democratic administration next time round,’ he says, ‘but what Bush has done to our world needs a lot of patching up.’ And: ‘We’ve spent so much money on this war our bridges are falling down. As far as the infrastructure goes here, healthcare should be dealt with in this next election.’ And: ‘I’m glad to see Mr Brown is not so comfortable with President Bush. I think he takes a stronger stand on things.’

The actor’s 24/7 interest in news and politics is reflected in his choice of films, which are often distinguished by some degree of political edge: the Bourne films with their indictment of the CIA; Sam Mendes’ war-is-idiotic Gulf conflict drama Jarhead; the oil business conspiracy tale Syriana; and the forthcoming Middle East-set murder mystery The Kingdom. And now Breach, of whose real world basis Cooper says: ‘I remember pretty clearly that it was quite a big piece of news. Only after three or four days of media coverage it disappeared. What I’ve since discovered is this turned out to be a real embarrassment for the FBI. I think they got a hold of the media and shut the story down.’

His great success in playing redoubtable political, military and other authority figures – and, increasingly, morally compromised characters such as Robert Hanssen – has inevitably led to Cooper being stereotyped to a degree by the film business. You want a crusty colonel or a secretive spook – call Cooper’s agent. ‘Honestly,’ says Cooper, ‘an actor really can’t forge his own path. These scripts come my way one at a time, and if I’m interested in what I’m reading that determines the course of events. It’s very linear. But I’m sort of putting out there a moratorium on military men, FBI agents and the like. I’ve been there, done that.’

Cooper’s looking for new pastures. His most enjoyable acting experience to date, and the one for which he was given the greatest amount of creative freedom, was playing John Laroche in Adaptation. ‘It was all such a joyful experience,’ he recalls fondly, ‘and in many ways a unique situation.’ Charlie Kaufman’s wildly original script, about a screenwriter trying and failing to write a film about a pirate-like purveyor of rare flowers, gave Cooper an unusual degree of leeway to interpret the character.

Accordingly, Cooper gave director Spike Jonze five different interpretations at a highly unorthodox audition, and nailed the part with his seductive if toothless buccaneer version.

‘It was such a different character from what I’d played,’ Cooper says. ‘I was fortunate to receive some recognition for that. At the same time that was the most comical character I’ve ever played, and I’m looking for that opportunity more, a lighter side. Down the road, I’d love to have the opportunity to play a real comedic character.’

It’ll come, no doubt. And on the back of the sombre likes of Robert Hanssen, Cooper doing comedy will be a genuine and pleasurable eye-opener.

Breach, Cineworld, 23 Aug & 24 Aug, 7pm, £7.95 (£5.50).