New York (Reuters) - Serena Williams's bid to break the professional era record for career grand slam titles came to a halt on Thursday when she was upset 6-2, 7-6(5) by Czech 10th seed Karolina Pliskova in the US Open semi-finals.

For top-seeded Williams, whose 22 grand slam titles are tied with Steffi Graf, it marked the second consecutive year she lost in the semis at Flushing Meadows while chasing history.

Williams came into last year's semi-finals as the three-time defending champion and two wins shy of a rare calendar-year grand slam but was upset by Roberta Vinci.