Katie Boulter was on the backfoot there, but Carol Young Suh Lee can't get her racquet up fast enough to defend the passing shot.

Match point.

Katie Boulter tried to come in for the inside-out forehand on Carol Young Suh's serve, but she can't move her feet quick enough and she skews the return wide.

She has better luck on the next serve though. Deuce.

Carol Young Suh Lee sends a serve out wide and blasts the return to the other side of the court, leaving Katie Boulter with no chance of getting there.

But the British number one is going nowhere. 30-30.

Heather Watson
British tennis player on BBC Radio 5 Sports Extra

Boulter is looking like she's injected the ball with more pace and she's just looking more confident and focused. Very locked in.

Lee's still fighting very hard and making her play the extra ball but Katie seems calm and collected now.

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Katie Boulter steps up the intensity again and whacks a volley winner home before sinking a drop shot into the net. 15-15.

Katie Boulter canters to a 40-0 lead before allowing Carol Young Suh Lee back in with a overhit forehand.

But the British number one finds her rhythm again and slams a winner past the American to move one game away from a place in the second round.

Five games on the spin. Can she make it six?

Heather Watson
British tennis player on BBC Radio 5 Sports Extra

Katie's doing a really good job of keeping the pressure on Lee here and keeping her foot on the gas pedal.

This time she gets it! A blistering cross-court winner and it's four games on the bounce for Katie Boulter.

I don't want to jinx things, but surely she can't lose this match now.

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"Let's go Katie" shouts a fan. The world number 62 has another break point after her opponent finds the net.

That's good anticipation there from Carol Young Suh Lee as she races to the corner of the court before Katie Boulter pins a forehand there.

But the American wildcard can't finish the job off and we go to a fifth deuce.

Nope. She puts Carol Young Suh Lee on the backfoot with a decent return down the line, but then she slices a backhand into the net. Deuce.

Here we go. Another break point for Katie Boulter. Can she get this one over the line?

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She cant' make that one count either. Another wide forehand from the British number one and we go to deuce.

That's a bad miss from Katie Boulter on the first break point, but she'll get another crack.

Katie Boulter is really going for her shots now. And it's paying off.

After sending one forehand wide, she ramps up the power again and Carol Young Suh Lee can't deal with it. Two break points.

A forehand by Carol Young Suh Lee loops long and Katie Boulter makes sure to slams the door shut with a strong second serve that Lee can only send beyond the baseline.

That 3-0 lead looks very healthy, but it's just the one break of serve that separates the pair as things stand.

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Katie Boulter broke early in the second set, but she allowed Carol Young Suh Lee straight back in. The Briton won't want to make the same mistake again.

Lee has got a half-chance here, though, at 30-30.

Carol Young Suh Lee saves the first break point with a solid serve, but she lets a forehand fly long on the next one.

An early break for Katie Boulter and that should give her a bit of a lift at the start of this deciding set.

Carol Young Suh Lee sends a winner sailing down the line but Katie Boulter replies with an epic cross-court forehand to bring up two break points.

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