Johanna Konta has recorded a three-set victory over Tsvetana Pironkova in the US Open second round, despite being on the brink of a withdrawal in stifling conditions in New York.

It appeared that the British number one would be forced to pull out of the last-64 contest after she struggled to breathe towards the end of the second set but after assistance from the doctor and trainer, she recovered to run out a 6-2 5-7 6-2 victor.

It was plain sailing for the 25-year-old in the opener as she broke the Bulgarian's serve twice and after striking again at the start of the second, she looked on course for a routine victory.

However, she was immediately broken back and in the 11th game that lasted almost 10 minutes, she dropped to her knees and was required to undergo treatment on the baseline before delivering a second serve to try to save a third set point.

Konta told the doctor that her body was "in shock" as her blood pressure was taken on court but despite being cleared to continue, she inevitably double-faulted to concede the set.

A fresh-looking Pironkova was a huge favourite to prevail but Konta broke in the first game after the restart and never looked backed as she managed to control her emotions and energy levels.

After breaking again for 5-2, Konta served out to love to set up - fitness depending - a mouthwatering showdown with young Swiss star Belinda Bencic.