Iga Swiatek reached the fourth round of the US Open last yearVenue: Flushing Meadows, New York Dates: 29 August-11 SeptemberCoverage: Daily radio commentaries across BBC Sounds and the BBC Sport website and app, with selected live text commentaries and match reports on the website and appWorld number one Iga Swiatek came out on top in a meeting of Grand Slam champions as she beat Sloane Stephens to reach the US Open third round.
Two-time French Open winner Swiatek beat American Stephens, who won the 2017 US Open, 6-3 6-2.
Swiatek will next face American Lauren Davis who beat 28th seed Ekaterina Alexandrova 0-6 6-4 7-6 (10-5).
Eighth seed Jessica Pegula and three-time finalist Victoria Azarenka also advanced on day four in New York.
Swiatek has won 52 matches this year, including a 37-match winning streak that included her French Open title win.
However, she has not gone beyond the quarter-final stage of a tournament since losing in the third round at Wimbledon in July.
Her best result at Flushing Meadows is a fourth-round showing in 2021.
American Pegula, who has reached the Australian Open and French Open quarter-finals this year, beat Aliaksandra Sasnovich of Belarus 6-4 6-4.
Belarusian Azarenka beat Ukraine's Marta Kostyuk 6-2 6-3.
Last week, Kostyuk criticised the decision to include Azarenka in a Tennis Plays for Peace exhibition match in the build-up to the US Open and subsequently rejected an invitation to play.
The United States Tennis Association (USTA) said the event was "supporting the humanitarian relief efforts" after Russia's invasion of Ukraine.
Azarenka later withdrew because of the "sensitivities to Ukrainian players", the USTA said.
Belarusian leader Alexander Lukashenko is a key ally of Russia.
Kostyuk held out her racquet for Azarenka to tap at the end of the match.
Czech 21st seed Petra Kvitova advanced after her Ukrainian opponent Anhelina Kalinina withdrew with illness, while Switzerland's Olympic champion Belinda Bencic beat Romania's Sorena Cirstea 3-6 7-5 6-2.
