Serena Williams overcame a huge scare to her Grand Slam bid, downing fellow American Bethanie Mattek-Sands in three sets to reach the US Open fourth round.
The world number one was broken at the first time of asking, and never drew level in the opening set, but she turned it around to post a 3-6 7-5 6-0 victory and prolong her historic attempt.
Serena was uncharacteristically nervy trying to close the second set, blowing a 5-3 30-0 lead as Mattek-Sands got back on serve.
And the underdog made Serena work for the set, saving two set points but not a third as the top seed got the match back on script.
Serena then went in for the kill in the third, losing only four return points as she put Mattek-Sands to the sword.
Next up for the 21-time major winner is another American, 19th seed Madison Keys, after the latter ousted Polish 15th seed Agnieszka Radwanska 6-3 6-2.
Earlier, Venus Williams proved too strong for 12th seed Belinda Bencic, whose fine North American swing came to an end with a 6-3 6-4 defeat.
Venus, the 23rd seed, made the fourth round or better in her first 12 appearances in New York, and after a four-year hiatus from the last 16, she is back there again.
Venus will next meet qualifier Anett Kontaveit.
Eugenie Bouchard pulled out a tough victory over Dominika Cibulkova 7-6 (11-9) 4-6 6-3, to earn a clash with Roberta Vinci for a spot in the last eight.
Bouchard, seeded 25th, saved five set points before winning the opener, only to blow a break lead in the second.
However, the one-time Wimbledon finalist overcame such a deficit early in the decider, losing the first game on serve but effecting consecutive breaks in response to win in two hours, 48 minutes.
Vinci, meanwhile, overcame a second-set slip-up to surpass Mariana Duque-Marino 6-1 5-7 6-2, and is within one win of her third quarter-final appearance at Flushing Meadows.
Kristina Mladenovic ended the run of lucky loser Daria Kasatkina with a 6-2 6-3 win, to reach the fourth round of a major for the first time.
Teenager Kontaveit, of Estonia, built on her already ground-breaking run, moving into the last 16 with a 6-2 3-6 6-0 win over local hope Madison Brengle.
Kontaveit, playing in just her third major, earned her first win at grand slam level earlier in the week, and will next take on two-time champion Venus Williams for a spot in the quarter-finals.
Mladenovic’s next hurdle is 13th seed Ekaterina Makarova, who overcame Elina Svitolina – the 17th seed – 6-3 7-5.