Top seeds Serena Williams and Novak Djokovic both advanced to the quarter-finals of the U.S. Open with straight-sets wins in their fourth-round matches Monday.

Williams, the women's No. 1, reached her first Grand Slam quarter-final of the year by defeating Kaia Kenepi 6-3, 6-3, keeping alive her hopes for a third straight U.S. Open title.

Williams won 12 straight points on her serve to start the match against the 50th-ranked Kanepi.

The American said she felt pressure to win in New York after losing in the fourth round of the Australian Open, the second round of the French Open and third round of Wimbledon.

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Serena Williams eyes a shot during her fourth-round match against Kaia Kanepi in New York City. (Julian Finney/Getty Images)

"I finally made a quarterfinal this year!" Williams said in her on-court interview, raising her hands to the cheers of the crowd in Arthur Ashe Stadium. "I think I felt it in my service game. I'm like, 'Can I please make it to a Grand Slam quarters this year?' So glad to do it in New York."

The 17-time Grand Slam champion next plays 11th-seeded Flavia Pennetta, a 7-5, 6-2 winner over 29th-seeded Casey Dellacqua.

Canada's Eugenie Bouchard, the seventh seed, lost to No. 17 Ekaterina Makarova on Monday. That left Williams and No. 10 Caroline Wozniacki as the only top-10 women's seeds remaining.

Under the lights Monday, Aleksandra Krunic tried to pull off another shocker against two-time U.S. Open runner-up Victoria Azarenka but couldn't quite do it. Azarenka, a two-time Australian Open champion, took four of the last five games to win 4-6, 6-4, 6-4.​

Djokovic cruises

Playing mostly mistake-free tennis, men's No. 1 Djokovic reached the quarter-finals in New York for the eighth year in a row — and 22nd consecutive Grand Slam tournament overall.

Djokovic, the 2011 champion at Flushing Meadows, made only 19 unforced errors, saved both break points he faced, and breezed past 22nd-seeded Philipp Kohlschreiber of Germany 6-1, 7-5, 6-4.

The last time Djokovic was eliminated before the quarter-finals at a major was a third-round loss to Kohlschreiber at the 2009 French Open.

Next up for the Serb, who reached the U.S. Open each of the past four years, will be a match against 2012 U.S. Open champion Andy Murray, who defeated ninth-seeded Jo-Wilfried Tsonga in straight sets.

Murray pulled out the sort of tough win he had been missing this year, beating Tsonga in three long sets.

The eighth-seeded Murray needed 2 hours, 35 minutes to defeat the ninth-seeded Frenchman 7-5, 7-5, 6-4 on a hot, humid Monday afternoon.

Tsonga had three break points to go up 3-0 in the final set, but Murray fought them off to swing the momentum. He promptly broke in the next game to get the set back on serve, and then closed out the match with another break.

"The first two sets were very long, tough sets, mentally very draining," Murray said in an on-court interview. "Glad to get through."

Elsewhere, fifth-seeded Milos Raonic of Canada fell to No. 10 Kei Nishikori of Japan by scores of 4-6, 7-6 (4), 6-7 (6), 7-5, 6-4 in a match that ended early Tuesday morning.

Australian Open champ Stan Wawrinka tumbled into the stands, kept calling for the trainer to treat cramping, and still pulled away to reach the quarter-finals. The third-seeded Wawrinka won 7-5, 4-6, 7-6 (7), 6-2 against Tommy Robredo.

Canada's Pospisil eliminated in doubles

Canadian Vasek Pospisil and his American teammate Jack Sock were eliminated in the third round of the men's doubles event, losing 6-2, 6-2 to Argentina's Carlos Berlocq and Leonardo Mayer.

Pospisil and Sock were the surprise champions at Wimbledon in July.

With files from The Associated Press