Coco Gauff overpowered Iga Swiatek on Sunday to help the United States retain the mixed teams United Cup title by beating Poland in the final.

World number four Taylor Fritz sealed the United States' second title in the 18-team competition after edging Hubert Hurkacz 6-4, 5-7, 7-6 (4) in the men's singles at Sydney's Ken Rosewall Arena.

The Americans added to their triumph in the inaugural tournament in 2023, while Poland fell agonizingly short for the second straight year.

All eyes were on the blockbuster women's singles match, with Gauff and Swiatek having enjoyed unblemished records through to the final.

World number three Gauff had only won two of her previous 13 matches against Swiatek, but did claim a confidence boosting victory at the season-ending WTA Finals.

They traded early breaks in a high-octane start marked by powerful groundstrokes and athleticism from both players. But Gauff's consistency wore down world number two Swiatek in a physical contest.

In her return from a one-month suspension for doping, Swiatek has had a heavy burden in the tournament and it seemingly took its toll when she required medical attention in the second set.

The five-time grand slam champion left the court briefly after the eighth game in the second set, but Gauff put one hand on the trophy for the Americans with a 6-4, 6-4 victory in one hour and 52 minutes.

Gauff's strong form will be an ominous warning for rivals ahead of the upcoming Australian Open, where she reached the semifinals in 2023.

"I have the belief that I'm one of the best players in the world and when I play good tennis I'm hard to beat," said Gauff, who won the 2023 US Open.

"Today I think I played some great tennis. I'm glad I was able to get a point for Team USA. It was tough today."

Fritz, last year's US Open finalist, had to battle past 16th ranked Hurkacz in a see-saw contest that had the fans at Ken Rosewall Arena on the edge of their seats.

The 27-year-old American's serve and powerful forehand helped him claim the first set before being pushed to the limit by a fighting Hurkacz.

It came down to a third set tiebreak with Fritz stepping up on the decisive points and he clinched his country's triumph with a forehand winner to trigger jubilation for the Americans.