Poland, US and Greece all won their city finals on Wednesday to progress to the semi-finals of the inaugural United Cup where they will be joined by 'lucky losers' Italy.
Matteo Berrettini edged the Italians ahead in their Brisbane final with a thrilling three-set win over Hubert Hurkacz but it was the Poles who came through to win the tie 3-2.
In the semi-finals, Poland will face the US, who saw off Great Britain in Sydney, while the Italians will face off against Greece who prevailed 3-2 over Croatia in their Perth final.
Thursday is a day off, allowing all teams to travel to Sydney where the semi-finals commence on Friday.
Poland came through their tense battle with the Italians thank to victory in the deciding mixed doubles, where Iga Swiatek and Hurkacz combined amid rain interruptions to beat Lorenzo Musetti and Camilla Rosatello 6-1, 6-2.
“Today’s match was pretty stressful because we [don’t] play mixed doubles usually," said Swiatek. "But I’m so happy that I was able to play a solid game and Hubi was pushing our opponents and really making it easy for me."
Musetti produced an almost flawless display of serving against Daniel Michalski to put Italy in front in the first singles match of the day.
The 20-year-old Musetti, who climbed to 23 in the world in 2022, blasted 17 winners past the 260th-ranked Michalsk to win 6-1, 6-1 in just 57 minutes.
"I was so focused today on the match and the serve was really good," he said. "But with every shot I had a great feeling for the ball so I think I played the best match so far."
Berrettini, who has slipped out of the top 10 after rising to six in the world, later produced an impressive 6-4, 3-6, 6-3 win over world number 10 Pole Hurkacz to give two wins to the Italian men.
Their women, however, were less successful with Martina Trevisan and Lucia Bronzetti swamped in straight sets by world number one Swiatek and rising star Magda Linette respectively.
"To win as a team is something special," said Hurkacz. "And having Iga as a partner the way she hits the ball, it’s just amazing. Definitely the girls carried the team today, so thanks for that.”
- US progress -
In Sydney, world number three Jessica Pegula put the United States 2-1 up over Britain when she crushed Harriet Dart 6-2, 6-0.
Pegula was ruthless in her 57-minute demolition of the 98th ranked Dart.
"I think I did everything really well today -- some days you come out firing and you feel really good," she said.
Madison Keys gave the United States an early lead before Cameron Norrie struck back when he won a high quality match against Taylor Fritz.
Keys lost the first set to Katie Swan before recovering to win a gruelling match 2-6, 6-3, 6-4.
Norrie and Fritz played an enthralling encounter which was in the balance until the Briton broke at 4-4 in the final set then served it out to claim a 6-4, 5-7, 6-4 victory.
Frances Tiafoe secured victory 3-1 with his 3-6, 7-5, 6-3 defeat of Dan Evans.
"Every time we play, we go to war," Tiafoe said. "He came out very hot.
"I served well and I'm just happy to get out of it. I'm happy the USA keeps going."
Pegula and Fritz closed out a 4-1 victory, defeating Dart and Evans 6-4, 6-4 in the mixed doubles.
- Greek grit -
Maria Sakkari and Stefanos Tsitsipas powered Greece through a marathon final, which finished shortly before midnight, to beat Croatia 3-2 in Perth.
World number six Sakkari and Stefanos Tsitsipas, ranked fourth in the men's game, combined to defeated Petra Martic and Borna Gojo 7-6 (8/6), 6-4 to claim the late night win.
“I’m happy we pulled this through. I’m proud of the team,” said Tsitsipas. “Fighters is what defines us."
Croatia's Donna Vekic had started with a defeat of Greek Despina Papamichail, losing just two games. Tsitsipas got one back for Greece, stopping Borna Coric 6-0, 6-7 (4/7/, 7-5.
The Croats took a 2-1 lead through Gojo, a 6-4, 6-2 winner against 803rd ranked Stefanos Sakellaridis before Sakkari squared the tie with a 6-3, 6-3 win over Martic.