Robert Redford didn't know Jane Fonda was in love with him.

The Hollywood icons have starred together a number of times since their first co-starring movie, 1967's 'Barefoot in the Park', but the 81-year-old screen legend had no idea the 79-year-old actress ever had feelings for him.

He told the Daily Telegraph newspaper: ''I didn't know she was in love with me.''

However, the movie veteran admitted he and Jane have always had effortless chemistry.

He said: ''There was just a chemistry we had as human beings that we could carry on to the screen that required no effect.

''And it's been that way through all of our films.''

Despite admitting her love for her co-star - who have starred as onscreen couples multiple times - Jane revealed the reason they never became a couple off screen was because they were both married.

One reason why Robert may have been oblivious to Jane's love for him was because he had a stand-offish attitude while shooting their films.

Jane recalled in their joint interview: ''Bob can be moody and back in the 1960s and 1970s when we worked together, sometimes he wouldn't speak to me all day, except for what was in the script.

''And I would think 'Oh my God, I've bothered him, he doesn't like me, I've done something wrong.''

But the pair are starring in a new Netflix drama 'Our Souls at Night' as a couple of a widowed elderly neighbours whose relationship leads to eventual sex, and had a much more ''fun'' time together than they used to.

Jane said: ''This time - and this is what's fun about it, that you can compare your experience now with back then - it was like 'Come on, Bob, lighten up!'

''Yeah, I could tease him. I didn't feel like it was my fault. And so I thought 'Oh, you know, I'm growing up'.''