SYDNEY, Australia -- Taylor Fritz clinched the United Cup title for the U.S. on Sunday evening when he defeated Matteo Berrettini 7-6(4), 7-6(6). Jessica Pegula and Frances Tiafoe had each earned a point for the Americans earlier in the day, giving their country an insurmountable 3-0 lead over Italy.

The United States produced a dominant performance throughout the United Cup, dropping only two individual matches. None of the ties were closer than 4-1.

Pegula gave her country a good start with a 6-4, 6-2 victory against Martina Trevisan. Tiafoe then surged through the first set against Lorenzo Musetti when the Italian retired trailing 6-2 with a right shoulder injury.

Despite the straight-sets score line, the first rubber was far from straightforward for the WTA No.3. Trevisan came out firing with an ultra-aggressive strategy and remained committed to front-foot tennis throughout.

Pegula, normally an excellent proponent of these tactics herself, found herself forced on to the back foot more than usual. Though she led 3-0 and then 4-2 in the first set, Trevisan managed to level at 4-4 after coming up with a series of sizzling forehands.

The set turned on a rare shot that Trevisan backed off. Serving at 4-5, 30-30, a tentative drive volley allowed Pegula to crunch a forehand of her own to reach set point. The American converted it with a superb backhand winner down the line.

Pegula settled in the second set, reducing her unforced error tally from 17 to seven while eliciting mistakes from Trevisan. Trevisan's do-or-die approach ultimately didn't pay off as the WTA No.27 racked up 31 unforced errors against 14 winners.

Trevisan went down swinging, finding another sequence of crowd-pleasing winners to cut Pegula's 5-0 lead to 5-2. But Pegula remained solid to close out the second set in an identical manner to the first: with a pinpoint backhand down the line.

Tiafoe picked up where Pegula left off, breaking Musetti's serve early and cruising through the opener 6-2, saving all three break points he faced. The Italian increasingly touched his right shoulder as the set wore on before receiving treatment from a physio during a changeover. At the end of the set, Musetti shook hands with Tiafoe and retired.

Fritz capped the team's run with a poised performance against Berrettini, who had earned Top 10 victories against Casper Ruud and Hubert Hurkacz earlier in the event. The American let slip all nine break points he earned, but did not let that hurt his play in the critical tiebreaks.

The reigning Indian Wells champion was steadier in those crucial moments, triumphing in 2 hours and 16 minutes.

Berrettini saved the first championship point he faced in the second-set tiebreak by crushing a forehand winner. But after switching sides, Fritz won a grueling rally to win what proved to be the deciding mini-break when the Italian missed a forehand on the full stretch.

Fritz capitalized on his second opportunity, and Team United States rushed from its Team Zone and tackled the 25-year-old to the ground in celebration.

With just points and prize money at stake in the fourth rubber, Madison Keys extended the U.S. lead to 4-0, while also preserving her own unbeaten record with a 6-3, 6-2 win over Lucia Bronzetti. The mixed doubles match was not played. 

Keys slammed 22 winners to Bronzetti's six, and 18 of her serves went unreturned -- including a service winner on match point.

Keys and Tiafoe, Team USA's No.2 players, both finished their United Cup campaign with a perfect 5-0 record. Pegula and Fritz went 4-1.

"Seeing these guys do their thing, it's special," reflected Tiafoe on the week. "Seing Fritz the last couple days play -- can't lose a tiebreaker, it's insane. Seeing Jessica give an absolute lesson to the World No.1 is crazy. Madison winning a huge match to get us over the line the other day against Great Britain, it's just crazy."

Pegula concurred.

"It's been amazing to spend time with these guys and start the year like this," she said. "It's been super fun and already super memorable."

The ATP Tour contributed to this report.