Brad Pitt says fatherhood is lots of fun and not bad for his work either, although forget about sleeping.

Pitt and his partner Angelina Jolie, with children in tow, came to Venice to promote his new film about Western outlaw Jesse James, which is competing for the top Golden Lion award at the city's film festival.

"It's the most fun I've ever had and also the biggest pain ... I've ever experienced," Pitt told a news conference Sunday when asked what it was like to become a family with four children in a short space of time. "I love it and can't recommend it any more highly — although sleep is nonexistent."

Pitt and Jolie have a 15-month-old girl, Shiloh, born to the couple. Jolie has also adopted three children close in age from Cambodia, Ethiopia and Vietnam.

Having four small children "makes me much more efficient because when I work, I really have to focus. I know I've less time to get things done. Actually, I'm quite pleased by it," said Pitt.

The actor described "The Assassination of Jesse James by the Coward Robert Ford," starring Pitt, Casey Affleck and Sam Shepherd, and directed by Andrew Dominik, as "more a gangster film than a Western."

Pitt plays James in the last year of his life as he lapses into paranoia over potential betrayal by accomplices and intimates.