American teenager Coco Gauff ended Caroline Wozniacki's fairytale return to the US Open on Sunday, booking her place in the quarter-finals with a three-set victory.

Sixth seed Gauff, regarded by many as one of the favourites for the title after two tournament wins in August, advanced to the last eight with a 6-3, 3-6, 6-1 victory on the Arthur Ashe Stadium court.

The 19-year-old will face either defending champion Iga Swiatek or Latvia's Jelena Ostapenko in Tuesday's quarter-finals.

"I knew going in I had to play aggressive," Gauff said after her victory. "I'm happy that I was able to get back and focus. 

"She's a player you have to be mentally tough with every single point."

The defeat ended former world number one Wozniacki's impressive showing at the tournament.

The 33-year-old retired after the 2020 Australian Open to start a family, and this year's US Open was only the third event the mother-of-two has played since returning to the tour in Montreal last month.

Gauff, who was only one when Wozniacki made her debut on the WTA in 2005, paid tribute to the Dane's performance in defeat.

"Caroline is back, it's like she's never left," Gauff said. "The level she played today was amazing, and she's been an inspiration for me growing up.

"I grew up watching her win the Australian Open...to be out on the court with her today was an honour."

After dropping the first set, wild card entrant Wozniacki had raised the prospect of a mammoth upset after punishing an error-strewn second set by Gauff to level at one set apiece.

A rattled Gauff was then broken in the opening game of the third set to deepen the jitters amongst the teen's fans.

But Gauff rallied to break back immediately and then turned up the pace to break Wozniacki for leads of 3-1 and 5-1 up before holding to clinch victory.

rcw/mw