Bradley Cooper is surprised by the controversy surrounding 'American Sniper'.

The 40-year-old actor stars in the Clint Eastwood-directed movie, which tells the story of the deadliest marksman in US military history - and has argued that ''any discussion'' about the ''plight'' of the nation's military should be welcomed.

He reflected: ''You never know when you make a movie if anybody's going to see it, so to have the audacity to think that it would cause any sort of effect at all would be pretty presumptuous.

''Any discussion that sheds light on the plight of the soldiers and the men and women in the armed services, for that discussion to occur is fantastic.''

Cooper has earned an Oscar nomination for his portrayal of Chris Kyle, but the film has also attracted criticism from the likes of Michael Moore and Seth Rogen.

Rogen compared the movie to Inglourious Basterds's Nazi propaganda film-within-a-film 'Nation's Pride'.

He explained: ''American Sniper kind of reminds me of the movie that's showing in the third act of Inglorious Basterds (sic).''

Meanwhile, Moore - an Oscar-winning filmmaker - said: ''We were taught snipers were cowards. Will shoot u in the back. Snipers aren't heroes. And invaders r worse (sic).''