Costner Wanted Princess Di in 'Bodyguard 2'

Aug. 5 -- Kevin Costner is opening up on the movie that never came to be — a sequel to The Bodyguard that he says would have featured Princess Diana as his leading lady.

In an exclusive interview on Primetime Thursday, Costner opens up about the new love in his life and takes on rumors that he's one of the toughest stars to work with.

He tells ABCNEWS' Diane Sawyer how he approached the Princess of Wales about succeeding Whitney Houston in a sequel to the 1992 blockbuster, and was working on the project up until the day Diana was killed.

"She was very quiet. She was really sweet. And I said, 'Yeah, there's going to be a kissing scene.' And she laughed," Costner says. "And we began to talk. And we had a couple of talks. And it was all really going that direction.

"There was a very real thing between us in terms of doing this movie," he says. "She hadn't said yes to it, but she had indicated to me that she knew her life was going to change."

Costner says he got the script for the film on Aug. 31, 1997 — the day Diana was killed in a Paris car accident.

‘I Don’t Suffer Fools’

After a series of box office disappointments, the 48-year-old star is looking forward to his latest directorial effort, the Western Open Range, which opens on Aug. 15.

The double Oscar winner has been one of Hollywood's most bankable leading men. But his last two features, Dragonfly and 3,000 Miles to Graceland, didn't fare well with critics or moviegoers.

As he seeks a comeback, Costner denies claims that he's difficult to work with, but says he does feel protective of his films.

"I don't suffer fools … I'm firm. I can't be budged around a lot, by something that I know to be true," he says. "I mean, movies are like patients that want to die, OK? You know, you have to watch them all the time … sometimes you have a real vision, you know, of what something wants to be, and all you're trying to do is just protect it."

Costner's optimism is buoyed by his fiancée, Christine Baumgartner. "The central thing maybe about her is that I don't covet anyone else," he tells Sawyer.