There she will meet local girl Jessica Pegula, who had more problems with the weather than her opponent as she cruised into the quarter-finals.

Pegula was up against two-time Wimbledon champion Petra Kvitova but she brushed her aside 6-3 6-2 to reach her third major quarterfinal of 2022, delayed only by a rain break.

Swiatek beat Germany's Niemeier 2-6 6-4 6-0, but is clearly not in the form that brought her 37 straight wins earlier this season.

Swiatek came into the US Open just 4-4 in her last eight matches but she hadn't lost a set at Flushing Meadows until Monday. Niemeier got the early jump -- as she exhorted the crowd to get louder -- and gamely tried for another grand slam upset. She knocked out No. 2 seed Anett Kontaveit in Wimbledon.

Swiatek steadied herself in the second set and hit ten winners, and she turned the third set into a rout. Swiatek became the first Polish woman to reach the quarterfinals at the US Open and is trying to become the first top-seeded woman to win it since Serena Williams in 2014.

Swiatek said: "I'm just proud that I didn't lose hope because she was playing really good in the first set. I'm pretty glad that I used my experience to keep the same kind of level throughout the whole match."

Pegula was held up for about 45 minutes at 1-1 in the first set while rain fell. There is a retractable roof at Arthur Ashe Stadium, but it wasn't closed until after a downpour soaked the court.

The US Tennis Association said in a statement that its "weather team" told US Open organisers there was no rain expected. The statement added: "Unfortunately, a pop-up sunshower occurred."

The No. 8-seeded Pegula is the highest-ranked American woman and the only player in the top 10 in both singles and doubles.

She reeled off the last three games of the opening set, which ended with a double-fault by No. 21 Kvitova, and then the last six games of the fourth-round match after trailing 2-0 in the second set.

Pegula is a 28-year-old who was born in New York State, albeit in Buffalo, 300 miles away. Her parents own the NFL's Buffalo Bills and NHL's Buffalo Sabres.

She is enjoying the extra support that brings, saying: "It's definitely different playing overseas, I feel people don't make the connection as often as they do here.

"There is a lot of people from Buffalo that are kind of all over the place, you always find somebody that's a Bills and Sabres fan.

"And to me I think I have more embraced it and find it fun and cool that these people, because there's not a lot of tennis in Buffalo, know nothing about tennis but they will come and watch the match in Cincinnati or here or wherever, just because they are a fan of the teams."

She is 0-3 in Grand Slam quarter-finals so far, including losses at that stage at the Australian Open in January and the French Open in June. The loss in Paris came against Swiatek.

With PA

Australian Associated Press