NEW YORK (DPA) - German veteran Andrea Petkovic danced on the court in delight as she upset sixth-seeded Petra Kvitova, 6-4, 6-4, on Thursday (Aug 29) for a place in the third round of the US Open.

Petkovic, 31, won the last four games from 4-2 down against the two-time Wimbledon champion to mark only the second tournament of the year in which she has won two main draw matches.

The former top 10 player Petkovic has slipped to an 88 ranking but has traditionally played well against Kvitova, who has rarely played lately owing to forearm injury problems. Petkovic had also won their previous duel at the 2018 Australian Open and leads their series 6-5.

"I feel so happy. Petra is one of my favourite players. It was a crazy end," Petkovic said on-court after fist-pumping and dancing when she clinched victory on Kvitova's miscued overhead shot.

"I had some ups and downs but was there in the most important moments."

Kvitova is the highest women's seed to bow out in New York, at the start of a busy day with 55 men's and women's second-round matches - after rain led to the postponement of 23 matches Wednesday.

Due on court later on a sunny day were among others world number one and title holder Naomi Osaka, three-time winner Rafael Nadal and teenage sensation Coco Gauff.