Top seed Simona Halep set up a highly anticipated Australian Open last-16 tie against Serena Williams by beating the American’s older sister Venus.

The 27-year-old Romanian eased to a 6-2 6-3 victory, winning in straight sets for the first time at this year’s tournament in Melbourne.

Seven-time champion Williams, 37, reached the last 16 by thrashing 18-year-old Ukrainian Dayana Yastremska.

“It’s going to be a bigger challenge but I’m ready to face it,” said Halep.

The Romanian says she has “nothing to lose” against the 23-time Grand Slam champion, who is aiming to match Australian Margaret Court’s all-time record of major triumphs.

Williams has won eight of their nine previous matches, with their last meeting coming at the US Open in 2016.

Since then, Halep has won her first Grand Slam title, having triumphed at last year’s French Open.

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Halep puts herself among the contenders

Halep, who lost to Caroline Wozniacki in last year’s final, said she came into the first Grand Slam of the year with “no expectations” after a difficult past five months.

She arrived in Melbourne having not won since August, a five-match losing streak punctured by an absence with a back injury, while she also split with her long-time coach Darren Cahill in November.

After needing her fighting qualities to beat Estonian veteran Kaia Kanepi and young American Sofia Kenin in the opening two rounds, Halep moved up a level against seven-time major winner Williams, 38.

“It was a great match – my best match here this year,” Halep said.

“It is always a big challenge to play against the Williams sisters so I was super motivated.”

Halep could not take any of three break points in Williams’ first two service games, yet was finally rewarded in the fifth game to lead 3-2.

After surviving four break points in the next game, Halep took control of the opener as Williams appeared to wane physically in a set containing some lengthy rallies.

The points became shorter at the start of the second, allowing Williams to stick with Halep as they stayed on serve to 3-3.

But when Williams failed to land a first serve in the seventh game, Halep pounced.

Two break points – added to the five she created in the first set – arrived and she upped the pace to force Williams into sending a weak backhand into the net on the first.

Serving to stay in the match, Williams produced two double faults to hand Halep two match points – but the Romanian only needed one and sealed victory with a stunning forehand down the line.

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Seven-time champion Serena Williams comforted opponent Dayana Yastremska after powering past the teenager into the Australian Open fourth round.

Williams beat the 18-year-old Ukrainian 6-2 6-1 in one hour and seven minutes and did not drop a service game.

“You’re gonna make it, don’t cry”, Williams, 37, told a tearful Yastremska following her victory.

The American will face Romanian world number one Simona Halep or sister Venus Williams in the next round.

“I thought she did really amazing,” Williams said when asked about the future of Yastremska, who was not even born when the American won the first of her 23 Grand Slam singles titles in 1999.

“She came out swinging and to be so young, she came out ready to go. When I was young I played against so many people and everyone I faced was intimidating and not easy. You just go out and swing and do the best you can.”

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Williams in the driving seat

Williams is favourite to win a record-equalling 24th Grand Slam singles title in Melbourne and her performance in the third round showed why.

She put youngster Yastremska under immediate pressure, breaking in the first game and winning four games in a row.

The occasion seemed to have got the better of the Ukrainian – a promising talent who could only provide brief glimpses of her ability and could not hide inconsistencies with her serve.

But Williams was ruthless and looks firmly on course to win a record-extending eighth Australian Open title.

With defending champion Caroline Wozniacki exiting on Friday and rivals Naomi Osaka – the fourth seed – and Elina Svitolina – the sixth seed – being forced to fight back to scrape their way into the fourth round, it is so far falling into place for Williams.

Her toughest test yet will be in the next round where a mouth-watering tie with either Halep or her elder sister awaits.

Williams joked that sister Venus “still intimidates me now” but that she is enjoying being back in Melbourne after missing last year’s competition four months after she gave birth.