Halep through to US Open semi-final

Simona Halep has booked her spot in the semi-finals of the US Open after beating Victoria Azarenka 6-3, 4-6, 6-4 in a rain-delayed clash.

It's the first time that Halep has made it to the last four at Flushing Meadows, and she will face up against Flavia Pennetta we beat Petra Kvitova in the day's first quarter-final.

The match started with successive breaks, with both players losing their first service games, though only Halep was able to manufacture a second break during a marathon fourth game that saw Azarenka fend off four break points before finally succumbing to the fifth.

Halep held on from there to go one set up, but Azarenka wasn't done fighting.

The two-time Australian Open champion broke early in the second set to race to a 3-0 lead and though Halep would hit back twice with breaks of her own, she could not make either of them stick, and Azarenka was able to level the scores at one set all.

There was another epic 20-minute game at the start of the third set, with Azarenka fending off three more break points in a 15-point game before holding serve. That resolve paid off as she seized the next game to go 2-0 up.

True to the see-saw nature of the game, however, Halep would produce a couple of stunning winners in the next game to get back on serve.

The players were forced off the court by rain, and after a lengthy delay of nearly an hour-and-a-half it was Halep who returned the stronger of the pair as both players looked to finish the match in a aggressive fashion.

Halep eventually managed to claim the decisive first set when she converted her ninth break point of the set to move 4-3 ahead.

The Romanian hung onto that advantage despite Azarenka going down swinging, with three unforced errors from Azarenka in the final game putting pay to her chances.

It was the first time since 1982 that all three of the women's quarter-finals have gone the distance, and after a gruelling fourth round match, Halep will be facing a race against time to return to full fitness, or close to it, ahead of her semi-final on Friday.