Kevin Costner has called his legal battle with actor Stephen Baldwin "frivolous" and "upsetting," but has vowed not to give up the fight.

Baldwin has filed a lawsuit against Costner, accusing The Bodyguard star of duping him into giving up his shares in a pioneering oil-cleaning technology.

Baldwin insists the actor persuaded him to sell up shortly before he found success with the oil-filtration device, using it to help clean up the Gulf of Mexico spill in 2010, and he is demanding $4 million.

The case is due to go to trial this summer, but Costner is adamant he won't give in and settle with Baldwin out of court.

He tells The Hollywood Reporter, "In my mind, it's a frivolous lawsuit. But I won't stop, no matter what. We have (oil) spills every day around the world. We don't have an adult response to how to clean it up."

"I knew how to do it 20 years ago in a very engineered, scientific way. But the oil industry didn't beat a path to my door. Twenty million dollars of my own money later, I have the Baldwin lawsuit, and it's completely upsetting to me."