Serena and Venus Williams set up a 30th career meeting on Wednesday as the US Open reeled from a sexism row sparked when a player changed her shirt on court.
In the men’s section, world number one and defending champion Rafael Nadal steamed into the third round on another scorching day with a straight-sets win over Vasek Pospisil.
Six-time champion Serena eased into Friday’s third round encounter against her sister with a 6-2, 6-2 win over German world number 101 Carina Witthoeft on the back of 30 winners and 13 aces.
Venus, the 2000 and 2001 champion, made the third round for the 17th time with a 6-4, 7-5 victory over Camila Giorgi of Italy.
Friday’s match will be the earliest the sisters have met at a Slam since the 1998 Australian Open in what was also their first ever clash. It will be their sixth face-off in New York.
Since Venus won their first ever clash in Australia, Serena, bidding for a record-equalling 24th Grand Slam title, has built up an advantage over the last two decades, enjoying a 17-12 head-to-head superiority.
Venus, 38, and playing her 80th Slam, notched up her 775th career win by seeing off Giorgi.
Defending champion and third seed Sloane Stephens also made the third round with a marathon 4-6, 7-5, 6-2 win over Ukraine qualifier Anhelina Kalinina.
Azarenka, the 2012 and 2013 runner-up, made the third round for the first time in three years with a 6-1, 6-2 win against Australian 25th seed Daria Gavrilova.
Azarenka was amongst the first players to condemn the United States Tennis Association (USTA) for handing French player Alize Cornet a code violation for changing her shirt on court on Tuesday.
The incident sparked an immediate storm over sexism.
The Belarusian said the USTA displayed double standards for sanctioning Cornet while male players routinely remove their shirts courtside when the heat and humidity bite.
The USTA admitted they were wrong to hand Cornet a warning for slipping off her shirt on court after realising she had put the garment on back-to-front during a heat-break.
Cornet said she was stunned that the furore had caused so much controversy and was happy to accept the USTA’s apology.
Meanwhile, Nadal, spared the worst of the heat thanks to his late-night start on Arthur Ashe Stadium, sped past Pospisil 6-3, 6-4, 6-2.
His only hiccup came in the second set, when he dropped his serve to fall 2-4 down.
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