Matteo Berrettini put Italy into the city final of the inaugural United Cup with a brilliant attacking win over world number three Casper Ruud in Brisbane on Tuesday, while Maria Sakkari helped send Greece through.
Berrettini broke Ruud once in each set for a clinical 6-4, 6-4 triumph that gave Italy an unassailable 3-0 lead over Norway.
Italy will play Poland in the Brisbane final, after the Poles completed a 3-1 win with Hubert Hurkacz beating three-time Grand Slam winner Stan Wawrinka 7-6 (7/5), 6-4 and Magda Linette stopping Jil Teichmann 5-7, 6-4, 6-1.
The winner of each city final in Sydney, Brisbane and Perth, along with the best-performing team from the beaten finalists, will play the semi-finals in Sydney.
Ruud, who had a brilliant 2022, went into the match as the slight favourite, but Berrettini was superb from the outset.
He served well throughout and his powerful groundstrokes put the Norwegian under enormous pressure. Berrettini hit 10 aces and eight forehand winners, with the power and placement of his shot-making causing big problems.
Berrettini, who has slipped to 16th in the world, said he knew he had to serve well against Ruud.
"He's improved so much in the last year so I knew that I had to serve my best," he said.
"We know each other pretty well so I knew I had to serve like that, but it's one thing knowing I had to and one thing doing it."
Lucia Bronzetti later made it 4-0 to the Italians with a 6-2, 7-5 win over Ulrikke Eikeri.
In Perth, world number six Sakkari ensured Greece moved through to the final when she downed Belgium's Elise Mertens 6-1, 7-5.
The Greeks went into the match needing to either win the tie or lose 3-2 to progress to the city final.
Sakkari's point made it 2-1 to Greece, cementing their position. Number 803 teenager Stefanos Sakellaridis played the match of his life to defeat Zizou Bergs 5-7, 6-1, 6-3.
Sakkari and Stefanos Tsitsipas finished off the tie 6-3, 6-2 over Kirsten Flipkens and Michael Geerts.
"I knew the match would be critical, so I was nervous, especially against a world-class player like Elise," Sakkari said.
"When you play a regular tournament and you lose, it's just for yourself, but I wanted to win today for the team more than myself.
"It means a lot to play for your country."
Greece will line up against Croatia, which defeated France 3-1.
- Croatia through -
Caroline Garcia kept the French in the chase with her 7-6 (11/9), 6-4 win over Petra Martic of Croatia.
But Borna Gojo came through against Adrian Mannarino 7-6 (7/5), 3-6, 7-6 (7/5) in a three-hour thriller which secured a Croat victory.
Gojo needed six match points to clinch the tie for his Balkan nation. He broke Mannarino at 5-4 as the Frenchman served for the match, taking the struggle into a winning tiebreaker.
"I won the match, but this is a team competition," the 144th-ranked Gojo said.
"I'm just a small part of it. We won today and we get to go again tomorrow,
"At 5-4 down I was trying to break back, I went for it and made a couple of amazing winners.
"I'm happy I stayed calm and finished it off in the tiebreaker."
In Sydney, world number three Jessica Pegula of the United States comprehensively defeated Germany's Laura Siegemund 6-3, 6-2.
"She's always really tricky. She's really feisty and has a lot of tools, but I think conditions are really fast here so I just tried to rush her and play my game," said Pegula.
"And I think I did that really well today."
Frances Tiafoe downed Oscar Otte 7-5, 6-4 to take the Americans 4-0 over Germany.
The United States, who had already qualified for the city final, will play Great Britain in the Sydney decider.