Serbia's Novak Djokovic reached the Olympic singles quarter-finals for a record fourth time by beating Germany's Dominic Koepfer 7-5 6-3 on Wednesday but looked in the mood to go much deeper in the tournament.

For all his 24 Grand Slam titles and countless other accolades, the Olympics has never been especially kind to the 37-year-old for whom a bronze medal remains his only souvenir.

Paris is most likely his last opportunity to fill the only unoccupied space in his bulging trophy cabinet and so far everything is going entirely to plan at Roland Garros as he is yet to drop a set in three rounds.

If he beats Stefanos Tsitsipas in the next round he will be in his fourth Olympic singles semi-final, although the only time that led to a medal was at the Beijing Olympics in 2008.

Eighth seed Tsitsipas, who beat Argentina's Sebastian Baez on Wednesday, will present a formidable obstacle having led Djokovic by two sets to love in the 2021 French Open final only to eventually succumb in five.

"I don't expect anything less than a big fight and a tight match," Djokovic said of Thursday's clash. "The goal is to get to the finals and have a battle for that gold."

All four women's singles quarter-finals were scheduled for day five and the first of them produced another shock in the women's draw as Slovakia's Anna Karolina Schmiedlova beat Czech Wimbledon champion Barbora Krejcikova 6-4 6-2.

Later, top seed Iga Swiatek of Poland was in action against American Danielle Collins.

After the emotions and hyperbole of Djokovic's previous round against his claycourt nemesis Rafa Nadal, the atmosphere on a muggy Court Philippe Chatrier was sedate as he comfortably dispatched 30-year-old Koepfer after some initial trouble.

Djokovic earned an early service break with an exquisite drop shot but handed back the advantage immediately.

Koepfer looked confident after four wins across singles and doubles so far in the Olympic tennis at Roland Garros but he undid all his good work at 5-6 down when a bungled drop shot attempt and an errant backhand handed Djokovic the set.

The German needed medical treatment early in the second set and his resistance quickly faded as Djokovic recorded his 16th career singles win at the Olympics -- the most by any player since tennis returned to the Games in 1988.

Second seed Carlos Alcaraz will also aim to reach the singles quarter-finals later when he plays Roman Safiullin before returning with Nadal for a doubles quarter-final.

There were mixed fortunes for American men on day five of the tournament as Tommy Paul ended French hopes of a medal by beating Corentin Moutet 7-6(5) 6-3 to reach the quarter-final but Taylor Fritz could not join him, going down 7-5 6-4 to Italy's Lorenzo Musetti.