NEW YORK • Johanna Konta collapsed to her knees midway through her match in stifling heat at the US Open on Wednesday before recovering to record an astonishing and controversial 6-2, 5-7, 6-2 win over Bulgaria's Tsvetana Pironkova.

A set up but fading physically as temperatures touched 30 deg C, Konta served facing set point. She fell woozily to the ground and was seriously distressed as she gasped for breath.

For seven minutes she sat on a towel with ice packs wrapped around her before waving away concerned attendants to sit on her courtside chair.

"I feel like my whole body is in shock," the 25-year-old was heard saying to the Women's Tennis Association's director of sports science and medicine, Elaine Brady. "I just started shaking, my heart rate went up and my vision became blurred. It was extremely scary."

The British 13th seed rose unsteadily and returned to double fault and surrender the set, then left the court to change her clothes before resuming.

Although still breathing heavily, she conjured a comeback, full of artful drop shots, lobs and passing shots, to win in 2hr 32min. She was so tired she could not celebrate.

If fit, she will take on Swiss Belinda Bencic in the third round today. Pironkova said Konta deserved her win but she described the conditions as "not that bad compared to other days".

She added: "What was frustrating for me was... the toilet break. Because I think the match was stopped for just too long."

THE GUARDIAN, THE TIMES, LONDON