Nadal led 6-4, 6-3, 2-6, 1-2 after 3 hours of play when the day’s second rain delay suspended the game, which will be resumed on Monday at 1100 GMT, AP reported.
Monday’s forecast predicts intermittent rain.
The French Open hasn’t been pushed past the final Sunday since 1973, when Ilie Nastase beat Nikki Pilic in a match that ended on Tuesday.
Djokovic is trying to become the first man in 43 years to win four consecutive Grand Slam titles. Nadal is seeking a record seventh French Open championship.