George Clooney plays his darkest role yet in 'The American'.

The Hollywood actor assumes his most brooding character to date in the film about a US hitman hiding out in an Italian village, and amazed the film's director Anton Corbijn with his "fabulous" performance.

He said: "George was into the role, which surprised me. Maybe it's because he's never played such a dark character. Perhaps in 'Michael Clayton' or 'Syriana' he was unsympathetic, but he's never been this harsh or unappealing.

"It was fabulous for me that he was able to go that dark. He does so much with so little. He was ideal."

Anton believes the film received a mixed reception from critics because people misinterpreted its style, admitting reviewers may have expected a blockbuster instead of something similar to the work produced by Italian spaghetti western filmmaker Sergio Leone.

He added: "I gave them Sergio Leone when some critics probably wanted Spider-Man 13. A lot of critics were angry.

"The trailer made it look like it was one thing - a fast-paced, popcorn, Hollywood thriller - when it was something else entirely. So when they got into the screenings and found that it was a European take on a western, they were furious."