No. 1 seeds Jannik Sinner of Italy and Poland's Iga Swiatek powered into the third round of the U.S. Open with commanding victories on Thursday.

World No.1 Sinner swept Alex Michelsen of the United States 6-4, 6-0, 6-2 in one hour and 39 minutes.

"It was a real improvement, for sure. I'm looking to get better now in the next days," said Sinner.

World No. 5 and 2021 champion Daniil Medvedev defeated Hungary's Fabian Marozsan in straight sets 6-3, 6-2, 7-6 (5) and moved into the third round.

In the women's draw, 2022 champion Swiatek cruised past Japanese qualifier Ena Shibahara 6-0, 6-1 in 65 minutes.

"I just felt the rhythm was much better. I was a bit tense in my last match, so today I just wanted to focus on the right things," said Swiatek.

China's Wang Xinyu lost to Yulia Putintseva of Kazakhstan 6-1, 7-6 (4) in the second round.

"I think I finally had the right tactic, I was trying to be everywhere and put some pressure on her," said Putintseva.

Two-time champion Naomi Osaka of Japan fell to 52nd-ranked Karolina Muchova of the Czech Republic 6-3, 7-6 (5).

"I think this year for me has been a learning year. I put a lot of energy and effort into all the tournaments that I played," said Osaka.