Poland and Australia have advanced to the United Cup semifinals in Sydney.

World No.1 Iga Swiatek propelled Team Poland into the United Cup semifinals for the second straight year by defeating China’s Zheng Qinwen 6-2, 6-3 in Perth on Wednesday.
 
Following the win by her fellow Top 10 Polish player Hubert Hurkacz in the opening men’s singles match, four-time Grand Slam champion Swiatek needed 1 hour and 34 minutes to beat Zheng and clinch the quarterfinal tie.
 
Poland, which lost to eventual champion United States in last year’s final four, will now travel from Perth to Sydney to compete in this weekend’s semifinals.

"I’m really happy with my game, and also how the atmosphere in the team is," Swiatek said on court after her win. "I really feel like we can just be better when we’re together, so for sure playing [with Hurkacz] is an exciting thing to do, and I’m real happy with every match that I play here."

Zheng, 21, ranked at a career-high No.14 and the 2023 WTA Most Improved Player, came into the match 0-4 against Swiatek but she had pushed her to a deciding set on three of those four occasions.
 
The top Chinese player went ahead by an early break on Wednesday and collect her first win over a reigning World No.1.

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But Swiatek regrouped, and from 2-0 down, she won the next six games to sweep through the first set. Swiatek went 3-for-3 on break points in the opener.
 
Zheng continued to battle in the second set, fighting back from 3-0 down and saving five break points in a gutsy hold for 3-3. 
 
However, Swiatek reclaimed the break at 5-3 with a sturdy return game, then converted her second match point to seal a trip to the semifinals for her nation. Swiatek won 80 percent of points when returning the Zheng second serve.

"I played up to my expectations in my singles," Swiatek said. "Qinwen put some pressure on me, especially at the beginning of the match, but I was able to go even a level higher. I'm happy with how I played."

 In the first match of the tie, Hurkacz moved Poland to the brink of the semifinals when he defeated Zhang Zhizhen 6-3, 6-4 and put his country 1-0 up.
 
Hurkacz swung freely throughout the 1-hour, 22-minute match in Perth, backing up thunderous first serves with big forehands to improve to 3-1 in the pair’s head-to-head record.

“It is always a tough match against him," Hurkacz said. "He can play amazing shots and is such a tough competitor. I am really happy with that victory today.
 
“I believe I have more in my game but I was really happy with my performance today. Iga is insane. She is going to fight really hard for Poland now."
 
Hurkacz is now 2-1 on the new season, having also defeated Thiago Seyboth Wild in Perth. Last year the 26-year-old clinched the second ATP Masters 1000 title of his career in Shanghai.

Katarzyna Piter and Jan Zielinski made it a perfect day for Poland, coming in to win the mixed doubles 6-3, 5-7, [10-7] over You Xiaodi and Sun Fajing.

In the evening session, Australia stunned Serbia to book the home team's spot in its first United Cup semifinal. ATP No.12 Alex de Minaur led the way with an inspired upset over World No.1 Novak Djokovic 6-4, 6-4. De Minaur delivered a top-class all-around performance, during which he won 33 of 34 points behind first serves, to notch the biggest win of his career in 94 minutes.

Ajla Tomljanovic followed de Minaur to seal the victory, defeating Serbia's Natalja Stevanovic 6-1, 6-1 to give Australia an insurmountable 2-0 lead.

Stevanovic, ranked No.184, was called on to step in for Olga Danilovic. Armed with a crafty slice-and-dice game, Stevanovic tested Tomljanovic's discipline and patience early. But the Australian was up to the task, especially after her confidence-boosting performance against No.5 Jessica Pegula on Tuesday.

Ranked No.292 after being sidelined by injury last year, Tomljanovic bounced back in November to notch an emotional title run at the WTA 125K in Florianopolis.

After breaking first for a 2-1 lead, Tomljanovic dominated the set to take it in only 31 minutes. She limited Stevanovic to just 14 points. The trend continued through the second set. Tomljanovic dominated with her forehand down the stretch to seal her first win at the United Cup and first win of the season.

Doubles No.1 Storm Hunter closed out the Australian sweep, teaming with Matt Ebden to win the mixed doubles 6-3, 6-3 over Dejana Radanovic and Nicola Cacic.