Allen admitted to The Guardian that he still has a desire for a "tour de force part" opposite Keaton, who the filmmaker dated in the '70s and cast in his movies Sleeper, Love And Death, Interiors, Manhattan, Radio Days and Manhattan Murder Mystery.
"I can't be the love interest anymore," Allen said. "I can't play opposite Scarlett Johansson, it's not appropriate. So what can I do? I'd love to have a wonderful tour de force part with Diane Keaton but the problem is... doing what?"
He continued: "Nobody wants to see two septuagenarians get it on. People may say they do but they don't. They want to see Leonardo DiCaprio chasing after Scarlett Johansson. They don't want me flirting with Diane Keaton."
Allen also disclosed that he will appear in an "amusing turn" in his upcoming Rome-set comedy. The 75-year-old last appeared in front of the camera in his 2006 movie Scoop.
The filmmaker's You Will Meet A Tall Dark Stranger opens in UK cinemas on Friday.