'American Sniper' was a life-changing experience: Bradley Cooper

Los Angeles: Actor Bradley Cooper says war drama 'American Sniper' was a life-changing experience for him.

Cooper, 40, who has been nominated for best actor Oscar for his portrayal of lethal Navy SEAL sniper Chris Kyle, said he was initially wracked with anxiety over whether or not he could succeed in the role.

"It was a life-changing experience, truthfully. Personally, you set goals for yourself always but this was a pretty tall order. I was nervous, I didn't know if I was going to be able to do it," he said.

"There were a lot of sleepless nights early on where I was really overwhelmed with the responsibility. Coming out the other side of that was a huge accomplishment and it always makes you stronger, whether you fail or succeed, you gain different things from that," he added.

The film is directed by Clint Eastwood.