Kiefer Sutherland has praised his ex-fiancée Julia Roberts for calling off their engagement just days before their planned big day.

The 24 star and the Pretty Woman actress began dating and became engaged after they met on the set of Flatliners in 1990, and made plans to marry the next summer.

The then 23-year-old actress decided to call off the wedding three days before they were set to exchange vows, which Sutherland has now said took "courage" to do.

Speaking to People magazine, the actor explained: "I think she was being realistic for herself and I think that's much better. I think it's hard to explain the pressure. We were young and we were both very much in love and we had decided that we wanted to get married.

"She was arguably the most famous woman in the world and this wedding that was supposed to be something between the two of us became something so big," he continued.

"It wasn't what she wanted to do in the end and I think it took a lot of courage, in amongst all that other stuff, to be able to say, 'I can't do this'. And I'm gonna leave it at that."

Roberts went on to marry country singer Lyle Lovett in 1993 but they split in 1995. She then tied the knot with cameraman Danny Moder in 2002 and they have three children together.

Sutherland married Kelly Winn in 1996 and they separated in 1999. He filed for divorce in 2004 it was finalised in 2008.