USA beat China to reach semifinals at United Cup in Perth

Stars Coco Gauff and Taylor Fritz put a halt to China's stirring United Cup campaign with victories in their singles matches on Wednesday as top-seeded USA powered through to the semifinals.

After finishing as the highest-placed group runner-up in Perth, China's chances of a quarterfinal upset were dealt a blow when in-form Gao Xinyu was forced to stand down due to injury.

Gao had brilliantly stepped up in place of world No. 5 Zheng Qinwen to beat Beatriz Haddad Maia of Brazil and Laura Siegemund of Germany in breakout performances.

Zhang Shuai, who replaced Gao, put in a gallant performance against Gauff at the RAC Arena and broke her three times in the opening set.

However, the world No. 3 responded to the challenge and stepped up her firepower along the baseline to eventually prevail 7-6 (4), 6-2 in one hour and 34 minutes.

"I felt like I couldn't get her on defense," 2023 U.S. Open champion Gauff said. "She was playing so aggressive on me and I felt like I had to go more on my second serves. I had to take my chances."

World No. 4 Fritz sealed a semifinal spot for the Americans with a commanding 6-4, 6-4 victory over Zhang Zhizhen in one hour and 20 minutes. The U.S. Open finalist served strongly and capitalized on an error-strewn performance from Zhang, who finished with a 1-2 record in the tournament.

In the third match of the mixed doubles, Desirae Krawczyk and Robert Galloway outlasted Sun Fajing and Zhang Shuai 6-3, 6(1)-7, 10-3.

Earlier in Perth, Kazakhstan took advantage of world No. 2 Alexander Zverev's withdrawal to end Germany's title defense. Zverev, a two-time grand slam finalist, pulled out due to a biceps strain in a concern ahead of the Australian Open.

Daniel Masur had the tough task of replacing Zverev and put up a fight, but Alexander Shevchenko rallied to secure Kazakhstan's spot in the final four with a 6-7 (5), 6-2, 6-2 victory.

World No. 6 Elena Rybakina had earlier put Kazakhstan ahead after a commanding 6-3, 6-1 victory over Siegemund to kick-start the knockout round.