Britain's Harriet Dart suffered a painful defeat as she lost to Ukrainian 19th seed Marta Kostyuk in the US Open second round at a sweltering Flushing Meadows.
The British number three, aiming to reach the third round for the first time in her career, produced an error-strewn performance in a 7-6 (12-10) 6-1 defeat.
Dart hit 10 double faults as an afternoon where she made an encouraging start quickly turned sour.
In tough conditions, the 28-year-old led by a break three times in the first set and could not convert any of the five set points she created in the tie-break.