John Cusack famously specialises in morally ambiguous types: the affable but opportunistic psychic stowaway in Being John Malkovich; the Jewish art dealer who strikes up a friendship with a young Adolf Hitler in Max; the likeably laconic hitman in Grosse Pointe Blank.

But in his latest role — as professional hitman Brand Hauser in War, Inc. — he is perhaps the most mixed-up of the lot. Another professional killer (“It seemed like a good idea at the time,” says Cusack in his deadpan drawl), Hauser is sent to bump off the prime minister of a fictional war-torn nation called Turaqistan. His false identity is almost as loathsome as his actual job: the frontman of the US corporation in charge of “reconstructing” Turaqistan, ie, wringing every last dollar out of the benighted place.

But somehow — mostly via the combination of wisecracking charm, bemusement and self-awareness that has served him so faithfully since his teen roles in Stand By Me and The Sure Thing — Cusack makes you root for the guy.

His slippery screen personae are all the more intriguing given that he is one of Hollywood’s more politically commited denizens.

A regular blogger for the Huffington Post website, he has been a vocal critic of the Bush Administration and chats as easily about US domestic policy as he does about his other love, 1980s punk.

Does he do lurid satires such as War, Inc. so that he can step into the shoes of those he despises? “I wish War, Inc. were satirical,” he says. “Unfortunately I don’t think it was; it almost couldn’t go far enough.”

So why do so many of his characters roam the grey areas? “It’s probably the lapsed Catholic in me,” reckons Cusack (he grew up in an Irish-American family in Chicago). Blogging and the like is “the easy stuff, it’s the day-to-day living that’s hard.

I have a sense of how complicit my silence is: I go on making movies, making money. Maybe there’s some tension there that I want to explore.”

Sometimes the commercial temptations prove too great. After a series of indies, rom-coms and thrillers that have failed to set the world alight (including War, Inc., which has gone straight to DVD in the UK), Cusack has signed up for his first mega-budget picture since Con Air (1997). Called 2012, it sounds like a horror about the London Olympics, but it’s actually an apocalyptic action epic by Roland Emmerich, the director of Independence Day.

Is there any rationale behind his decision to re-embrace the blockbuster? “The rationale is it’s good to be in a big hit movie!” he chuckles. “Good for your career, and it’s nice to be wanted.”

Even so, he can’t resist raising a metaphorical eyebrow at the ambition of Emmerich’s special effects: “It’s one of those scripts where they have one line: ‘Rome burns’. An entire city! I was like: ‘How would you show that?’ But Roland says: ‘Oh yeah, it’ll be great’.” Cusack, we trust, will be the one with the fiddle.

Name your favourite . . .

Musical artists

Joe Strummer I actually did a blog about him after he passed away. For me it was just the idea that rebellion, anger was only the first step. He was trying to get you to use anger to propel you into a better, more creative world.

The Specials When I was young there were these bands like the Specials and Fishbone that were so great. So many things were still divided by religious and class and race lines, but they gave you a feeling of intelligent unity that you didn’t get in your normal life. And they were great fun.

Elvis Costello The ferocity of his intelligence, his personality and his talent was so wild. He was just a force.

Bob Dylan I’m getting very into his radio show.

The Ramones They‘re great but I talk about them partly because people keep on asking me about them in interviews — it’s a bit of a self-perpetuating thing. It’s not like I live in 1989 . . .

Regina Spektor Which new music do I like? Regina Spektor’s fantastic: poetic and weird and unique. And Black Rebel Motorcycle Club are great.

Things about Chicago

Barack Obama These days it feels like Chicago’s the centre of the world because the President is from there. I sure wouldn’t want to swap places with him, but he seems to be doing a reasonable, thoughtful job so far.

Music Great blues and jazz. And [Pearl Jam frontman] Eddie Vedder’s from Chicago, isn’t he?

Upton Sinclair I read quite a lot of his stuff after seeing There Will be Blood.

The Cubs and White Sox baseball teams The worst press I get these days is not because I’m attacking the capitalist war machine, it’s because I like both the Cubs and the White Sox. I have an excuse because I did a movie about the White Sox, Eight Men Out, so I got very into their lore. And when I was a kid growing up in Chicago, it was pre-cable, we only had a few channels and they had both teams on television a lot. I’m a huge baseball fan so I watched both the Cubs and the White Sox. People don’t buy that explanation, but it’s true.

Political figures

Franklin Roosevelt He’s the guy I’m thinking about a lot these days, given that the Obama Administration are trying to come up with a new New Deal.

Lyndon Johnson I was a fan of what he tried to do with the Great Society. What Obama’s creating is a lot more like that, but I fear if he doesn’t extricate himnself from Afghanistan, it could be his Vietnam.

Malcolm X Would I have him over Martin Luther King? No, you need them both, right? Who’s closer to my personal philosophy? [Laughs] I would never put myself in the same sentence as people like that! I wouldn’t dare.

Nelson Mandela Another massive figure of the 20th century.

Winston Churchill I don’t know why but I’ve been thinking about him lately too. He held things together, just through his sheer will, his personality and his oratory.

Films you have made

Grace is Gone (2007) A pretty sweet little movie. There wasn’t a climate in Hollywood at the time for those kind of films, but it pleased my stubborn, salmon-swimming-upstream nature.

Max (2002) I love that film. There were a lot of ideas that were pretty provocative.

The Thin Red Line (1998) I’m not in it that much so I don’t have to watch myself. It was some sort of three-hour tone poem, or something, with the sections rolling in and out of each other. I enjoyed it.

Grosse Pointe Blank (1997) Yeah, that one was good.

High Fidelity (2000) That was a good experience — we sort of got away with that one. I always tell Stephen Frears, I’ve got to do a move that can give me street cred. You work with Stephen, you get the street cred.

War, Inc. (2008) It’s got a pulse to it. A pretty insane film.

War, Inc. is out now on DVD

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