Simona Halep

The world No 1, who had won the pair's only previous meeting at Indian Wells in 2013, has endured her travails in the opening week in Melbourne, she suffered an ankle injury in her first-round victory, but remains in with a chance of a maiden Grand Slam title.

Halep, 26, served for the match on three separate occasions in the decider but was pushed all the way by her unseeded American opponent in a 4-6 6-4 15-13 victory, which lasted three hours and 44 minutes.

The unseeded French player, who won the Wuhan Open last week, edged the Romanian in a hard-fought battle, 6-4 7-6(3), in Beijing for an 11th straight match victory.

Halep, currently ranked No 2, defeated the unseeded Daria Kasatkina 6-2 6-1 to close in on the top spot held by Garbine Muguruza.

Muguruza's world No 1 position is under threat after she bowed out of this tournament in the first round with a virus.

Halep beat Maria Sharapova in the previous round and, after winning her quarter-final, will play Jelena Ostapenko who beat her at the French Open earlier this year.

The Romanian was given a scare by Roberta Vinci earlier in the tournament but was in prime form in her quarter-final on Thursday.

She swept past American Coco Vandeweghe 6-1 6-1 in just under an hour, breaking five times and not losing her own serve.

Halep will now face Latvian Anastasija Sevastova in Friday's semi-finals after the World No 22 saw off Kiki Bertens 6-3 6-3.