China's Zheng Saisai upset the newly crowned Olympic women's singles gold medalist Monica Puig of Puerto Rico to lead three Chinese women into the second round of the US Open at the USTA Billie Jean King National Tennis Center on Monday in New York.

Zheng, the world's No 61 player, defeated No 32-seed Puig, the surprise winner of the gold at the recently concluded Rio Olympics, by a 6-4, 6-2 score in one hour, 19 minutes in front of a boisterous pro-Puig crowd.

"It's always tough first round to play with anybody, especially she just won the Olympic gold medal," said Zheng. "It was also a lot of pressure for her (Puig) today.

"The crowd was really crazy for her. I think I executed my plan well today. I change a lot the high and the low, the fast and the short, and it worked very well today."

Zheng, 22, enjoyed her own success at the Olympics, upsetting No 4 seed Aga Radwanksa.

Puig was the first athlete to win an Olympic gold medal representing Puerto Rico and was showered with accolades and media attention much of the last two weeks leading into the Open.

"All credit to her, she played well," said Puig, of Zheng, while also admitting that she felt the pressure of increased expectations. "She complicated me just enough."

Zheng benefited from Puig's 28 unforced errors.

"I am very calm before the match," she said. "I wanted to enjoy the match. That is why I was not so nervous today."

Zheng will look to reach the third round at a Grand Slam for the first time against No 59 Kateryna Bondarenko.

Duan Ying Ying, ranked No. 103, also advanced into the second round Monday with a 6-4, 4-6, 6-3 win over Maria Sakkari of Greece.

Wang Yafan, the world No 163 who advanced into the tournament via the qualifying rounds, registered a 6-3, 7-6 (7-4) win over Alison van Uytvanck of Belgium.

China has six entries in women's singles. Wang Qiang, the world No. 62, Zhang Shuai, the world No 51, and Peng Shuai, the 2014 US Open semifinalist coming back from back surgery, are in action on Tuesday.

No Chinese men qualified for the men's singles field.