NEW YORK, NY, USA – Serena Williams’ ambition of securing a record-tying 24th Grand Slam title remains alive at the US Open as she moved into the quarterfinals with an immensely hard-fought 6-3, 6-7(6), 6-3 victory over No.15 seed Maria Sakkari.

It took Serena two hours 29 minutes to secure a last-eight matchup against Tsvetana Pironkova, who overcame Alizé Cornet, with the six-time winner extending her record to 105 wins to just 13 losses at major play at Flushing Meadows.

Success, though, was far from straightforward against Sakkari, who was seeking to become the first Greek player to make a Grand Slam quarterfinal, having also fallen at the last-16 stage of the Australian Open, where she pushed Petra Kvitova to three sets.

The WTA World No.22 threatened to repeat her come-from-behind victory over Serena in the Western & Southern Open on Grandstand Court less than a fortnight ago but was unable to deny the American her 100th win on Arthur Ashe and a 53rd Grand Slam quarter.

“I thought about it, but ever so little. But it’s a completely different match and a completely different scenario, a completely different moment. I kept fighting,” she said.

“She was doing so well, she was being so aggressive, and I knew I needed to do the same thing.”

No.3 seed Serena Williams remains on course for a seventh victory at Flushing Meadows - and a 24th Grand Slam title overall - after overcoming No.15 seed Maria Sakkari in three tough sets.

Indeed, it was Sakkari who dominated the early stages of the match, outhitting Serena and sending a message to her storied opponent by delivering three aces in her opening service game of the match.

Game five proved to be a turning point. Serena struggled with the afternoon sun shining straight in her face and fell 0-40 down, yet a combination of gritty play and a couple of unforced errors allowed her stave off the first break points of the encounter.

Perhaps shaken by this scare, the 38-year-old cranked up her pace in the following game. Having trailed 40-15, she prevailed in an arm wrestle from deuce to take the upper hand in the opening frame.

The players exchanged service holds, but Serena had no problems closing the set out, doing to in emphatic fashion with an ace down the ‘T’ that was swinging away from her opponent.

Unshaken by losing the opener, Sakkari responded positively to pressurize Serena at 30-30 at the beginning of the second, but two big serves would dig the American out of trouble.

Indeed, it was this ability to land punishing first serves was a key factor, particularly as the 25-year-old was beginning to make greater inroads when presented with a second delivery to face.

The first 11 games passed without a break point, although they were not without glimmers of opportunities, with Sakkari twice forced to defend from deuce before successfully recovering from 15-30 down when Serena would have served for the match had she failed.

A fortunate bounce off the net in the 12th finally brought an opportunity to break for Sakkari, only for Serena to deliver an unreturnable serve. Moments later, a similar scenario played out after the North American had netted a backhand. Fittingly, it was an ace out wide on the advantage court that booked the tiebreak.

Sakkari raced into a 4-0 lead only to be drawn back to within a point, yet a stunning backhand down the line restored some of her cushion, but Serena turned up the heat to level at 6-6 with some clutch tennis. A missed return, however, brought up a third set point, which proved telling as the match was levelled.

She maintained the momentum into the early stages of the decider, securing an early break, but Serena, who has now gone the distance seven times in nine outings since the Tour’s suspension ended, showed impressive resolve in the face of her opponent’s onslaught by hitting back.

It was experience and determination that ultimately told. At 3-3, 30-30, Serena sent down a thumping serve that equaled her fastest of the tournament, and she used that as a foundation not only to finish off the game, but also to break her opponent.

Victory, which was sealed at the second time of asking, was greeted with an almighty cry, testimony to how close Sakkari had been to halting her dream for the week but also to Serena's fitness levels.

“I’m definitely match fit. I’ve played a lot of three sets, so that’s also good because I’m not only match fit, I’m fit fit,” she said before revealing an unusual reason she is missing the fans.

“I miss the fans, but this is different. It’s also different because the breaks are a little bit longer when the fans are here because of the clapping. I could’ve used a little bit of that in this match!” she joked. “I love having the fans here, so I miss it.”

2020 US Open highlights: Serena battles past Sakkari