Serena and Radwanska into last 16
Three-time women's champion Serena Williams went level with sister Venus on 61 US Open career wins when she coasted into the fourth round of the US Open on Saturday.
Olympic and Wimbledon champion Williams won eight games in succession to claim a 6-4, 6-0 win over Russia's world 42 Ekaterina Makarova, the woman who knocked her out of the Australian Open this year.
Williams, the fourth seed, fired 31 winners and eight aces and will next face unseeded Czech Andrea Hlavackova, who beat Maria Kirilenko of Russia, the 14th seed, 5-7, 6-4, 6-4.
"After 4-4, I started to play better and more consistent. She's a good opponent, she beat me in Australia so I knew I needed to play better and I did," said Williams, the 1999, 2002 and 2008 champion.
Hlavackova, the world number 82, and making her US Open main draw debut, will be playing in her first Grand Slam fourth round.
Polish second seed and Wimbledon runner-up Agnieszka Radwanska matched her best US Open performance by also reaching the last 16 with a 6-3, 7-5 win over error-plagued Serb 30th seed Jelena Jankovic, the 2008 runner-up.
Radwanska goes on to face Italian 20th seed Roberta Vinci for a place in the quarterfinals.
Vinci reached the last 16 for the first time with a 6-2, 7-5 win over Slovakia's 13th seed Dominika Cibulkova, a quarterfinalist in 2010.
Former world number one and 2008 French Open champion Ana Ivanovic reached the last 16 for the fourth time with a 6-7 (4/7), 6-4, 6-2 win over highly-regarded American teenager Sloane Stephens.
The Serb 12th seed will next face Bulgaria's Tsvetana Pironkova who saw off Spain's Silvia Soler-Espinosa 6-1, 6-7 (3/7), 6-3.
German sixth seed Angelique Kerber, a semifinalist in 2011, eased past Olga Govortsova of Belarus 6-1, 6-2, and now meets French Open runner-up Sara Errani, the 10th seeded Italian, who defeated Russian qualifier Olga Puchkova 6-1, 6-1.
