Ashleigh Barty has passed the sternest test yet of her US Open title credentials to equal her best-ever run in New York.

Barty delivered a serving masterclass class to reach the last 16 for the second straight year with a composed 7-5 6-3 victory over rising Greek Maria Sakkari on Friday.

The win puts Barty on course for another blockbuster encounter with Serena Williams should they both win their next game and advance to the quarter-finals.

Sakkari, seeded No.30, beat Barty last year in Indian Wells, but Australia’s world No.2 played the match on her terms from the outset.

The French Open champion fired down 10 aces and dropped serve only once while breaking Sakkari four times during the 87-minute work-out on Louis Armstrong Stadium.

“This is an incredible court. New York is an incredible city and last year I felt like an adopted American playing with Coco (Vandeweghe) in the doubles, so I’m glad you haven’t forgotten,” Barty said after enjoying clear crowd favouritism during the match.

“Maria is an incredible competitor, a great mover around the court and plays her best tennis when she’s on the move and so it was important for me to try and dictate without going into her patterns,” she added.

“It’s tricky to play a friend, but I was really happy with the way I was able to close out those two sets.”

Barty will next face either 18th seeded Qiang Wang of China or unseeded Frenchwoman Fiona Ferro next on Sunday, with the winner likely strike Williams in the last eight.

Continuing her relentless quest for a record-equalling 24th grand slam singles title, eighth-seeded Williams swatted aside Karolina Muchova 6-3 6-2 in her third-round match.

Barty and Williams were also slated to meet in the Wimbledon quarter-finals, only for then-world No.1 Barty to suffer a shock fourth-round loss to unseeded American Alison Riske.

Alex de Minaur, meanwhile, claimed the biggest win of his career to surge into the fourth round at Flushing Meadows for the first time.

De Minaur wowed fans with a 6-2 6-4 2-6 6-3 triumph over seventh-seeded former Open runner-up Kei Nishikori.

The pulsating victory – his first over a top-10 rival – leaves de Minaur one win away from a potential quarter-final showdown with Roger Federer.

The watershed win also atoned for a gut-wrenching five-set loss at the same stage last year to Marin Cilic, the Croatian who beat Nishikori in the 2014 US Open final.

De Minaur is proving a crowd favourite at Flushing Meadow. Photo: Getty

“The crowd support was amazing,” said de Minaur, who has become a fan favourite in New York for his high-energy approach to the game.

“I’m just proud that I can go out here every day and move as I do and try to make as many balls as possible.

“I’ve been here (before), had a bit of a thrill against Cilic – was two sets to love up against him and I’m just glad I could get the win today.”

The winner of hardcourt titles in Sydney and Washington this year, de Minaur has earned himself a huge opportunity to make his maiden grand slam quarter-final.

He next plays Grigor Dimitrov or Polish qualifying lucky loser Kamil Majchrzak on Sunday, with the victor to face either Federer or the winner of Friday’s third-round match between David Goffin or Pablo Carreno Busta.

-with AAP