The father of Chris Kyle, the deadliest sniper in US history, told Clint Eastwood that he would face 'Hell' if he damaged his son's reputation in the new film based on his life.

According to the Daily Mail, Wayne Kyle warned the director: "Disrespect my son and I'll unleash hell on you."

Bradley Cooper plays Kyle in the forthcoming film American Sniper. Both Cooper and Eastwood assured Kyle senior that they would not do anything to cause distress to the family in the depiction.

"They looked me in the eye and told me they would honour my son's memory, “ declared 65-year old Kyle. “That was good enough for me. Both Mr Eastwood and Mr Cooper were men I could trust. They were very open and engaging and did not want to hide anything."

Kyle was a United States Navy SEAL and the most accomplished sniper in U.S. military history with at least 150 kills in Afghanistan and Iraq. He was shot dead at a Texas shooting range in 2013, along with a friend. The man accused of the killing is scheduled to stand trial for murder in February.