Josh Harnett says new film is hard to watch

Josh Hartnett is warning fans his new film Black Hawk Down is difficult to watch.

The movie is set to premiere at the Empire Cinema in London's Leicester Square.

It is based around America's military action in Somalia.

"Don't go into it thinking that you're going to be chewing your popcorn down and drinking your drink," Josh said.

"You're probably going to be swept up into something that is going to be hard to watch.

Stars expected at the London premiere include cast member Ewan McGregor and Ioan Gruffud and the film's director Ridley Scott.

Black Hawk Down is tipped to pick up a clutch of Oscar nominations when they are announced next month.