The second-seeded Federer was a game from losing the first set to Marcel Granollers in the third round Sunday when play was stopped because of lightning.
The sisters are bidding for their 14th Grand Slam doubles title, but first at Flushing Meadows since 2009.
10th seed Caroline Wozniacki dazzled on the Ashe Stadium Court in the third set, beating 5th seed and 2014 French Open champ Maria Sharapova 6-4, 2-6, 6-2 to advance to the quarterfinals.
Wozniacki beat the five-time major champ 6-4, 2-6, 6-2 in 2 hours, 37 minutes on a steamy Sunday.
The No. 1-ranked and No. 1-seeded Williams has faced American opponents in all three of her matches this week while extending her overall winning streak at Flushing Meadows to 17.
“Qualifiers” are gaining additional notoriety in the women’s draw.
Second-seeded Roger Federer of Switzerland has not won a grand slam in the US Open in more than two years, and at 33, some have wondered whether his time might be up.
Sara Errani, the No. 13 seed from Italy, and Venus Williams played what was the most exciting set of the US Open so far.
Two points from defeat, Sara Errani rallied to force a third-set tiebreaker and outlasted Venus Williams in a back-and-forth match at the U.S. Open.
It’s been a pleasure to watch such a young girl play her heart out, surprising herself with her first-round win and all the attention it garnered.
CiCi Bellis started nervously, then won seven games in a row during one stretch, but in the end, was beaten 6-3, 0-6, 6-2 by 48th-ranked Zarina Diyas of Kazakhstan.
Ivanovic, who had been having her best season since winning the French Open in 2008, lost to Karolina Pliskova 7-5, 6-4 in the second round Thursday.
Two-time champion Venus Williams won a place in the third round of the U.S. Open Wednesday night for the first time since 2010, a year before she announced she had been diagnosed with an autoimmune disease.
Sloane Stephens has carried the burden of being considered the possible successor to top- ranked Serena Williams for a while now. It’s either too much pressure for her, she’s not hungry enough or she doesn’t want it bad enough.
Maria Sharapova rallied from a set down to overcome a shaky serve and advance at the U.S. Open.