Throughout my interview with Alejandro Gon zález Iñárritu I wonder - as one does when in close proximity to a rather charming Hollywood director - what it would be like to be married to him. Being Mrs Iñárritu would have its advantages: the dark, grizzled good looks, the globe-trotting lifestyle, the pay packet. Yet, on balance, I decide it would probably be a nightmare. If living with the man is anything like watching one of his films, every day must be an emotional roller-coaster.
Iñárritu's three features - he now calls them a trilogy - have revolved around chance incidents that send the lives of his protagonists spiral ling out of control. In his debut, Amores Perros (2000), a car crash disastrously linked three sets of people from different social strata of Mexico City. Dark, bloody and beautiful, the film transformed him into what was, at the time, a rare beast: a Mexican director with Hollywood clout (he is now in good company, with the recent successes of Guillermo del Toro, director of Pan's Labyrinth, and Harry Potter's Alfonso Cuarón). Success did nothing to blunt Iñárritu's edge: his next film was the equally harrowing 21 Grams, starring Naomi Watts as a mother stricken by grief after losing her husband and daughters in another car crash.
This month brings the UK release of Babel, the third and most ambitious part of the trilogy. Where Amores Perros took Mexico City as its subject, Babel takes the world: it was shot in four countries and five languages. It stars Brad Pitt and Cate Blanchett as a couple hit by disaster while travelling across Morocco. Interlinking stories focus on two young Moroccan brothers from a Muslim family, a deaf-mute Japanese teenager and a Mexican nanny - all of whom, in their own ways, confront misery and death. Although Iñárritu himself contends that it is "a film about hope" (he said that about 21 Grams, too), by the end you feel you have been privy to a long scream of pain. Humanity is so vulnerable, so misguided, and the world so horribly unfair. It is also possibly the best film you will see all year: searing, ambitious and provocative cinema.
The man sitting in front of me, looking composed as he pours tea and nibbles on a posh biscuit, does not look like a frequent visitor to the depths of despair. He is tanned and svelte, and his black curly hair is carefully oiled back. His teeth have a certain Los Angeles sheen, as if they have been straightened or whitened, and an expensive-looking grey scarf is tied raffishly around his neck. He may have grown up in a poor barrio of Mexico City, but Iñárritu now looks every inch the polished Hollywood big-shot. His perspective on America, however, remains defiantly that of an outsider.
"I don't think of my work as being within the American tradition, which is the cinema of entertainment," he says. "Lots of people don't go to the cinema to see films which make them question. My films make you think, but most of all they make you feel. Some people love that, and some people hate it."
He is right. His work, perhaps particularly in the more reserved cultures of the north, is something of an acquired taste, the antithesis of the kind of subtle European cinema that thrives on repressed sentiment and emotional grey areas. "Emotion dominates my way of being. I would sometimes like to be more rational, but my nervous system works before my intellectual system," he says. "My cinema is an extension of my life. I express myself in the cinema, and making a film is like leaving myself naked. When I am filming these scenes [of grief] I suffer a lot, because what you film in the morning you also take to bed with you, and that's difficult. I am a very intense person - just ask my wife."
Babel unashamedly takes on not just one lofty theme, but a whole bunch of them. Iñárritu wanted to "talk about the overreaction of the [US] empire towards the Muslims. I also wanted to observe the problem of the borders between the United States and Mexico, and to talk about the millions of Mexicans who live a very harsh reality in America. I was interested in solitude, and deserts - not only actual deserts, but also urban deserts, where you are surrounded by people but totally isolated."
The new film returns to a question raised in 21 Grams: how do you measure the value of a human life? "The New York Times says that 3,000 Americans have died in Iraq, and 600,000 Iraqis. Imagine if that number of Americans had died. It is inconceivable. The value of American lives is [high], but in Africa, a million people can die and there's no reaction." Perhaps unsurprisingly, this message has had a mixed reception in the States, where the film premièred in October. One critic objected to "Iñárritu and [his screenwriter Guillermo] Arriaga's aggressive suggestion that we Americans and white Europeans are something less than exemplary citizens of the world, particularly in times of crisis". It was a response that came as little surprise to the director. "Unfortunately, there is a certain type of American who thinks that this film is a criticism, when it's not. It is simply a commentary on the reality," he says. "It is a very American sentiment, which interprets any kind of criticism as an attack. It's like the position of Bush: you're either with me or against me; there's no dialogue. Many people have felt attacked - sadly, because it was never intended to be an attack."
As the title suggests, one of Babel's central conceits is the difficulty of cross-cultural communication. But although the encounters between cultures in it are characterised by fear and mistrust, all the characters have the same fundamental priorities: family and the search for love. Like Iñárritu's previous two films, it is fundamentally about "parents and children, that is the nucleus. And through this microcosm you can observe the macrocosm; you do a biopsy on the cell to see how the body is working."
It is, perhaps, a simplistic vision that steers well clear of areas of deep inter-cultural conflict such as religion. But it is one that Iñárritu insists cinema can and should articulate. "The beauty of cinema is that it is the universal language," he says. "I decided to make this film using very few words, as I was striving for a very pure kind of film. The visual language takes audiences, without words or translations, into places they could never reach in reality."
Babel was shot in Japan, Morocco, the United States and Mexico, using local crews and casts of actors and non-actors. The biggest challenge, says Iñárritu, was getting underneath the rigidity of Japanese culture, so alien to his expansive Latin American sensibilities. "Moroccans are pretty much like Mexicans - lots of disorder, chaos, generosity. The third world is all the same. Japan is almost like another planet.
"I spent a lot of time just observing and absorbing, trying to think about things from the perspective of a native. I work very well in the abstract: there will come a moment when I just get something, its essence, almost like a smell. It's something I have inside, and I know when I see it and when I don't."
Paradoxically, the film has engendered communication problems of its own, prompting a breakdown in the relationship between Iñárritu and Arriaga, his long-time collaborator and screenwriter for all three films in the trilogy. The two men travelled the long road from Mexico City to Los Angeles together - Arriaga also recently wrote the screenplay for Tommy Lee Jones's critically acclaimed Three Burials of Melquiades Estrada - but Mexican cinema's most dynamic pairing has not survived the journey. Iñárritu reportedly banned Arriaga from the Cannes Film Festival première of Babel because he had claimed too much of the credit for the success of 21 Grams. It's a story that the director does not deny.
"We have had creative and personal differences, definitely, yes," he says. "But that is normal within the nine years of a creative relationship. Everyone wants to concentrate on the ending and not on what we produced during that time. It is natural that we both want to do other things. We are not married, after all. Guillermo wants to direct; he's producing his own film. I'm working on a project with another writer. I think that is healthy."
He does, however, make it clear that he considers Babel to be his baby. "I conceived the idea and invited Guillermo to work on it. He liked it, and presented me with some storylines . . . I suggested characters like the Mexican childminder and the deaf-mute Japanese girl. We carried on discussing and developing the idea for two years. My work is to provoke him, to stimulate him."
Iñárritu also made last-minute changes to the story: the trouble between Richard (played by Pitt) and Susan (Cate Blan chett) was originally the result of an infidelity, but he insisted the storyline be changed to the death of a baby (he and his own wife lost a two-day-old son some years ago). "Having Brad Pitt play an unfaithful husband seemed very obvious. I changed it because the loss of a son is deeper, and less ordinary."
While Arriaga's mettle has already been tested with The Three Burials, Iñárritu is still to prove that he can sustain his vision working with a different writer. He assures me that his next film, about "how the past projects itself on to the present", will be no less ambitious than Babel.
"I like to complicate my life, and have that possibility of failing. Sometimes when you fail it can be beautiful. You can learn things that nobody could ever tell you. It's a type of experience that makes you wiser, more prudent, more humble, and more human."
"Babel" is on general release from 19 January
González Iñárritu: a brief history
1963 Born in a "humble" barrio of Mexico City.
1979 After being kicked out of school, takes odd jobs as a commercial sailor and grape picker.
1984 Gets a job as a DJ presenting a three-hour show on WFM, Mexico's leading rock station; later directs and produces.
1986-92 While working at WFM, composes soundtrack for Garra de tigre as well as a number of other Mexican films.
1990 Joins the television channel Televisa. By age 27, has become one of its youngest artistic directors.
1991 Founds his own company, Zeta Films, to develop advertising and short film projects.
1995 Directs his first half-length feature, Detrás del dinero, a made-for-TV drama starring the Spanish singer Miguel Bosé.
1999 After 11 years writing a series of short films on different facets and contradictions of life in Mexico City, Iñárritu and the novelist Guillermo Arriaga decide to use three scripts as the basis for a feature film, Amores Perros.
The partnership was always an explosive one. Before they met, Iñárritu had offended Arriaga by criticising the university at which he taught. Arriaga said: "I used to say to myself, if I ever meet this guy, I'm going to tell him 'fuck you'."
2000 Amores Perros wins the Critics' Week Grand Prize at Cannes, making Iñárritu and Arriaga big names in the industry.