Defending champion Daniil Medvedev says fans can expect the unexpected when he meets fellow firebrand Nick Kyrgios in the US Open last 16 in New York.

Both players have a reputation as being combustible and are not afraid to speak their minds to umpires or even fans.

"On the court we never really had any fight or anything, which can change any moment," said Medvedev.

The 26-year-old Russian, who has lost three of the pair's four meetings, added: "You never know what's going to happen in the future, we are both quite electric.

"I don't think we are friends. When I say 'friends', we haven't been to the bar together but I feel like we respect each other a lot.

"It's 3-1 to him but I'll try to do better this time and it'll be a great match for people to watch."

Medvedev has had spats with Flushing Meadows crowds in the past, although he seemed to have won them over by reaching the 2019 final and beating Novak Djokovic in last year's final to lift his maiden Grand Slam title.

Australian Kyrgios, meanwhile, has courted countless controversies, and has already been fined $7,500 this week for spitting and swearing in his win over Benjamin Bonzi - after which the Wimbledon runner-up complained that a fan was smoking marijuana.

"I know a lot of people hate my game, the way I do things, they way I go about it," said 27-year-old Kyrgios, who beat Medvedev in their most recent meeting at the Canadian Open in August.

"I always thrive on it. I never want to forget all the things people say. I always carry this chip on my shoulder.

"I have it all in the back of my head when I'm playing. I want to be there. I want to be on prime time. I want to be on that screen, the screen they're all watching."

Defeat for Medvedev, who is yet to drop a set after three matches this week, would mean he will lose his world number one ranking after the US Open.

"He managed to get the better of me there (Montreal) for sure, especially I would say in terms of clutch moments," Medvedev added.

"I know what I have to do. Serve well, try to get to the tie-break, try to get opportunities on his serve. He also knows what he will do. Hopefully I can play my best game."

Fifth seed Casper Ruud's meeting with unseeded Frenchman Corentin Moutet begins Sunday's action on the Arthur Ashe Stadium at 17:00.

Andy Murray's conqueror Matteo Berrettini opens play against Spaniard Alejandro Davidovich Fokina at 16:00 on Louis Armstrong Stadium, which later hosts 12th seed Pablo Carreno Busta against 27th seed Karen Khachanov.

In the women's last 16, fifth seed and Wimbledon finalist Ons Jabeur's match with Veronika Kudermetova follows Medvedev-Kyrgios in the night session on Arthur Ashe.

Earlier on Sunday, 18-year-old American Coco Gauff faces China's Zhang Shuai and Alison Riske-Amritraj plays France's Caroline Garcia before Ajla Tomljanovic - who ended Serena Williams' career - takes on Liudmila Samsonova.