Australian Open champion Caroline Wozniacki beat Australian Sam Stosur 6-3 6-2 to reach the second round of the US Open in New York.

Second seed Wozniacki, 28, broke the 2011 champion’s serve three times in the first set and twice in the second.

The Dane will play Ukrainian Lesia Tsurenko in round three.

Fifth seed and two-time Wimbledon champion Petra Kvitova beat Belgian Yanina Wickmayer 6-1 6-4 at Flushing Meadows.

The Czech, 28, broke serve twice to take the first set and won five successive games from 4-1 down in the second. She will face China’s Yafan Wang next.

Kvitova, who reached the quarter-finals in 2017, said: “I’m not really looking too much ahead. I played great tennis here last year and it was amazing for me.

“So far this year it has been great too. It is good to be in the second round of another Grand Slam and to be playing good tennis.”

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Latvian 10th seed Jelena Ostapenko, the 2017 French Open champion, beat Germany’s Andrea Petkovic 6-4 4-6 7-5 to set up a second-round meeting with American Taylor Townsend.

Japan’s Naomi Osaka, seeded 20th, defeated German Laura Siegemund 6-3 6-2 and will play Romani’s Monica Niculescu or Israel’s Julia Glushko next.

Wimbledon champion and fourth seed Angelique Kerber will face Russia’s Margarita Gasparyan on Louis Armstrong.

Top seed Simona Halep was knocked out in the first round on Monday.