Daniil Medvedev upset defending champion Carlos Alcaraz in an enthralling semi-final duel to reach the US Open final on Friday.

Aryna Sabalenka fought back from the brink of defeat to overcome American 17th seed Madison Keys in a third-set tie-break and line up a US Open final against home favourite Coco Gauff.

The US Open was plunged into chaos on Thursday after environmental activists disrupted play, forcing a 49-minute stoppage as the tennis showpiece became the latest high-profile sporting event to be targeted by protesters.

American teenager Coco Gauff shrugged off a 50-minute stoppage caused by climate protesters to power into the US Open final on Thursday with a straight sets defeat of Karolina Muchova.

Defending champion Alcaraz moved to within one win of a potential dream final with Novak Djokovic with an emphatic straight sets victory over German 12th Alexander Zverev.

New York has been sweltering in a heatwave this week, with high humidity and temperatures at Flushing Meadows on Wednesday hitting 35 degrees Celsius (95 Fahrenheit)

Djokovic shrugged off ninth seed Fritz 6-1, 6-4, 6-4 to extend his dominance of American players in New York and take another step closer to a record-extending 24th men's Grand Slam title.

Daniil Medvedev expects his US Open quarterfinal with fellow Russian Andrey Rublev on Wednesday to be a real fight but said nothing will come between the childhood friends once the dust has settled.

Defending champion Alcaraz, who has only dropped one set on his journey into the last eight, produced a dominant display to overwhelm Italian world No.61 Matteo Arnaldi, winning 6-3, 6-3, 6-4 in 1hr 57min.

Defending champion Iga Swiatek was sent crashing out of the US Open on Sunday, losing in three sets to Latvia's 20th seed Jelena Ostapenko.

A tenacious Novak Djokovic survived a US Open late-night fright battling back from two sets down to tame fellow Serb Laslo Djere 4-6, 4-6, 6-1, 6-1, and 6-3 on Friday, and move into the fourth round at Flushing Meadows.

Romanian Sorana Cirstea sent big-hitting fourth seed Elena Rybakina tumbling out of the U.S. Open with a thrilling 6-3 6-7(6) 6-4 victory late on Friday to reach the fourth round at Flushing Meadows for the first time in her career.

Coco Gauff won the final 10 games of her match against Elise Mertens, completing a 3-6, 6-3, 6-0 comeback and reaching the US Open round of 16, where she will face Caroline Wozniacki on Sunday.

Defending champion Carlos Alcaraz eased into the third round of the US Open with a 6-3, 6-1, 7-6 (7/4) win over South Africa's Lloyd Harris on Thursday.

The 26-year-old from Shanghai -- ranked 67th in the world -- produced the match of his life to defeat last year's US Open finalist 6-4, 5-7, 6-2, 0-6, 6-2 in 3hr 19min.

The second-seeded Serbian superstar, eyeing a record-extending 24th Grand Slam singles title at these championships, booked his place in the last 32 with a 6-4, 6-1, 6-1 victor

Former U.S. Open champion Stan Wawrinka said he still had the game for the grandest stage after the Swiss veteran became the oldest man to win a singles contest at the tournament since a 40-year-old Jimmy Connors in 1992.

Alcaraz, returning to the same Arthur Ashe Stadium court where he lifted his first Grand Slam as a teenager a year ago, was always in control after Germany's Dominik Koepfer rolled his left ankle badly in the opening game

The 43-year-old tennis icon was no match for her 26-year-old opponent, who was born just weeks before Williams played her first Grand Slam final at the US Open in 1997

Novak Djokovic made a winning return to the U.S. Open by storming past Frenchman Alexandre Muller 6-0, 6-2, 6-3 on Monday to reclaim the world number one ranking and take the first step towards matching Margaret Court's record haul of 24 Grand Slams.