Briton Harriet Dart's first appearance in the US Open main draw ended in a straight-set defeat in the first round.
The 23-year-old lost 6-3 6-1 to Romanian fellow qualifier Ana Bogdan.
Dart was one of four Britons in action on day one of the final Grand Slam of the year, with Johanna Konta, Dan Evans and Cameron Norrie all playing.
World number 139 Dart, who had come through three rounds of qualifying, sent a forehand into the net on 26-year-old Bogdan's third match point.