Coco Gauff and Iga Swiatek are on a collision course for United Cup glory after the USA and Poland won their respective semifinals on Saturday in Sydney.
Swiatek beat Elena Rybakina to help last year's runners-up Poland see off Kazakhstan and they were joined in Sunday's final of the mixed-teams tournament by the Gauff-led United States.
The Americans defeated the Czech Republic, with Gauff beating Karolina Muchova and then an increasingly irate Tomas Machac retiring from his match against Taylor Fritz in an abrupt and bizarre ending.
"I woke up so late today," said Gauff, 20, after she dismissed Muchova 6-1, 6-4 to underline what a threat she will be at the Australian Open starting next week.
Gauff, the world No 3, added: "The whole match I was intense and focused, that made the difference today."
Big-serving Fritz, ranked fourth in the world, looked poised to level up their men's singles match after losing the first set when a hot and bothered Machac shook hands, sending the Americans through.
Five-time Grand Slam champion Swiatek played a starring role for Poland in their semifinal against Kazakhstan as she beat Rybakina 7-6 (7/5), 6-4.
"This win makes me really proud," Swiatek said after giving Poland an unassailable 2-0 lead in the tie.
"It is perfect preparation for the Australian Open," said the world No 2.
Swiatek again played with strapping on her right thigh, having been troubled in her tough three-set win over Britain's Katie Boulter in the quarterfinals.
That clash lasted nearly three hours and Swiatek was slow out of the blocks against Rybakina, who is ranked sixth in the world.
They went to a first-set tie break after Rybakina saved two set points, before the 23-year-old Pole pulled away to take her country into the final.
"I for sure did not start well and had the handbrake on a bit. I knew I had to do something and change the momentum," said Swiatek, who made light of any injury concerns.
She is relishing the prospect of a meeting with Gauff.
"I think at this stage she's developing every month and it's going to be also a nice challenge," she said.
Hubert Hurkacz put Poland on the way when he beat Alexander Shevchenko 6-3, 6-2 in the men's singles.
The 16th-ranked Hurkacz lost both his singles matches in group play but defeated Britain's Billy Harris in the quarterfinals and took that momentum into the meeting with Shevchenko.