Novak Djokovic remained comfortably on course for a first Olympic gold medal to add to his record-breaking collection of titles on Wednesday as fellow superstars Rafael Nadal and Carlos Alcaraz aimed for a place in the doubles semi-finals.

Djokovic, who has won three of his 24 Grand Slam titles on the clay courts of Roland Garros, defeated German left-hander Dominik Koepfer 7-5, 6-3 to become the first man to reach four Olympic singles quarter-finals.

The 37-year-old Serb has only ever collected a bronze at the Olympics, back in 2008 at Beijing, but he was rarely troubled on Wednesday by his 70th-ranked opponent, whose challenge eventually fizzled out.

"I'm soaking wet, honestly," he said. "It's a very, very humid day as it was yesterday. I just hope it rains so it cools down the temperature a bit and the air.

"But it is what it is. You have to kind of accept and embrace the conditions and it's the same for you and your opponents so you have to try to make the best out of it."

Djokovic, who had breezed past old rival Rafael Nadal in the second round, goes on to face 11th-ranked Stefanos Tsitsipas, the Greek he defeated in the 2021 French Open final.

Later Wednesday, French Open and Wimbledon champion Alcaraz tackles Roman Safiullin, the 66th-ranked Russian playing in Paris as a neutral.

Safiullin stunned Alcaraz at the Paris Masters in straight sets in 2023.

Defending champion Alexander Zverev, the third-seeded German, faces Australia's Alexei Popyrin while fourth-seeded Daniil Medvedev, also competing as a neutral, faces Canada's Felix Auger-Aliassime.

- Nadalcaraz -

Nadal plays for the fifth successive day as he and partner Alcaraz eye a place in the men's doubles semi-finals.

Nadal, a 14-time French Open singles champion on the clay courts of Paris, is chasing a third Olympics gold medal after pocketing the singles title in Beijing in 2008 and doubles in Rio eight years later.

The Spaniards face a tricky last-eight tie against fourth seeds Austin Krajicek and Rajeev Ram of the United States.

Both have enjoyed Grand Slam success, with Ram winning four doubles titles at the majors and Krajicek lifting the Roland Garros title in 2023.

Iga Swiatek, the four-time French Open champion, can claim a 25th successive win at Roland Garros by making the semi-finals of the Olympics for the first time.

The world number one from Poland has not dropped a set so far and takes on Danielle Collins of the United States.

Swiatek's path to a first gold medal was eased on Tuesday when world number two and US Open champion Coco Gauff was eliminated.

Three-time major winner Angelique Kerber, who will retire once her Olympics involvement ends, comes up against Zheng Qinwen, the Chinese world number seven.

Zheng made the quarter-finals in a tense three-hour win over Emma Navarro on Tuesday, after which the vanquished American accused her of being a "cut-throat" with "no respect".

Wimbledon champion Barbora Krejcikova faces Anna Karolina Schmiedlova, who stunned French Open and Wimbledon runner-up Jasmine Paolini in the third round.

In the remaining women's quarter-final Ukraine's Marta Kostyuk faces Wimbledon semi-finalist Donna Vekic of Croatia.