Serena Williams advanced to the second round of the US Open tennis tournament after straight-sets win against Danka Kovinic on Tuesday.

Williams, 407th in world rankings, secured a straight set win with the sets of 6-3 and 6-3 at New York's Arthur Ashe Stadium.

She will face No. 2 seed Anett Kontaveit from Estonia in the next stage.

The 40-year-old Williams has clinched 23 Grand Slam titles, including six US Open singles championships.

Leylah Fernandez, Ons Jabeur, Madison Keys, and Harriet Dart have qualified for the second round after beating their opponents.

In men's singles, Daniel Elahi Galan, ranked 94th in the world, defeated fourth-seeded Stefanos Tsitsipas 3-1 to advance to the next stage.

Dominic Thiem faltered in surprise defeat to Pablo Carreno-Busta as he lost the game with the sets of 7-5, 6-1, 5-7, 6-3.

Brandon​​​​​​​ Holt, Felix Auger-Aliassime, Alex De Minaur, and Nick Kyrgios have also qualified for the men's singles second round.