Camila Osorio actually throws her racquet to try and get something on that drop shot by Aryna Sabalenka, but she can't make contact.

At least the Colombian is smiling.

Camila Osorio can't catch a break from these Aryna Sabalenka forehands and the Belarusian now has two chances to restore her double break lead.

A swat of a forehand winner from Sabalenka saves the first break point, but that's an unfortunate time for the Belarusian to double fault.

That's a break rescued by Osorio, which has not improved Sabalenka's mood...

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A shake of the head and a few muttered words from Aryna Sabalenka as two missed backhands send her 15-30 down in this latest service game.

Oh, shot! Glorious up the line winner from Camila Osoiro, who almost ends up doing the splits as she retrieves the ball, and this is a couple of break back points...

Camila Osorio fends off a break point on her way to deuce, but she can't wriggle out of the game, and that's a double-break lead for the world number one.

It's also messy from Peyton Stearns in her opening service game of the second set.

A double fault is followed by an ace before two backhand errors present Harriet Dart with two break points - can she pounce this time?

Yes, she can! On the approach, Dart places a backhand volley into a wide open court.

The British number five backs it up with a hold to 15. We're back on serve.

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Unforced errors are flying from Harriet Dart's racquet as she's broken to 15 in the opening game of the second set.

Peyton Stearns has converted two of her six break points. Dart is 0/4.

Aryna Sabalenka finds a way through in the end to back up the break and stay in front.

Camila Osorio can't make the most of the first break point, but she stops Sabalenka from wrapping up the hold by finding the line with another brilliant winner.

The double faults are flying. This time it's Aryna Sabalenka's turn and she's not best pleased with herself.

That forehand winner down the line from Camila Osorio won't do much to improve the Belarusian's mood.

Harriet Dart saves two set points with consecutive forehand winners - the second a thunderbolt of a short cross-court return - before Peyton Stearns nets a routine forehand and smacks her racquet in frustration.

At the fourth time of asking, the American clinches the opening set 6-3.

Aryna Sabalenka won't get an easier break of serve. Five double faults in two service games for Camila Osorio and that one proves costly.

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A yell of despair from Aryna Sabalenka. That's a poor miss from the world number one and we're back to deuce.

But not for long. Yet another double fault from Camila Osorio.

Camila Osorio goes a little too big on the second serve, double faulting to hand Aryna Sabalenka the first break point of the match.

Trailing 40-15, Peyton Stearns buries a forehand winner before an untimely double-fault from Harriet Dart ushers in duece.

The Briton sends a simple forehand long at advantage and although she saves a break point to force a third deuce, she can't hold off the American. Down-the-line forehand for advantage before Dart's backhand abandons her.

Stearns will serve for the opening set.

Camila Osorio has less luck on serve. Aryna Sabalenka is returning well and she stays alive in the game thanks to a timely backhand winner down the line. Deuce.

A comfortable opening service game for Aryna Sabalenka. Two aces, one unreturnable serve and then a serve-volley combo to finish it off.

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Since winning the 'Sunshine Double' at Indian Wells and Miami in spring, Aryna Sabalenka has a 17-7 win-loss record.

That includes a chastening French Open quarter-final exit and a disheartening defeat in the Wimbledon fourth round.

And she hasn't had the best of build-ups to this year's US Open with early losses in both Cincinnati and Toronto.

However, Sabalenka has not lost in the first round of a Grand Slam in almost seven years and she has reached the fourth round in her last 17 major appearances.

What happened there?! After pushing the ball into the net again, Aryna Sabalenka completely mis-hits Camila Osorio's next serve and sends the ball flying skywards on Arthur Ashe Stadium.

Some very early signs of frustration from Aryna Sabalenka as she pelts the ball into the net.

But she pulls us back to deuce with some massive forehands that Camila Osorio can't cope with.