New York: Defending champion Marin Cilic was the first man through to the US Open tennis championship quarter-finals on Sunday, taking down determined Frenchman Jeremy Chardy 6-3, 2-6, 7-6 (7-2), 6-1 to extend his Flushing Meadows win streak to 11 matches.

Coming off a punishing five-setter with Mikhail Kukushkin in a third-round match that lasted four hours, Cilic took a while to find his power game, but was unstoppable once he did. The ninth seeded Croat blasted 23 aces past 27th seed Chardy, who had no answer.

"Key today was finding my rhythm on the serve, especially towards the end of the third set," said Cilic. "I was having trouble a little with my movement after I twisted my ankle in the second set. That was causing me a little trouble, but in the end it's pretty good. I played really good in the fourth set, really great tennis, so I'm happy about it."

Venus Williams reached the quarter-finals here, with a 6-2, 6-1 rout of Estonian teenager Anett Kontaveit on Sunday.

In women's doubles, top seeds Sania Mirza and Martina Hingis romped into the quarter finals with an easy 6-3, 6-0 win over 13 th seeds Michaella Krajicek and Barbora Strycova.

Cilic has found the defence of his title much tougher than winning, at least so far.

In last year's march to the title, Cilic recorded straight-set wins over Tomas Berdych in the quarters, Roger Federer in the semi-finals and Kei Nishikori in the final.

This year, with the exception of a straight sets decision over Russian qualifier Evgeny Donskoy, all of Cilic's matches have gone four sets or more.

After splitting the opening two sets, Cilic's power began to show through particularly in the third set tiebreak when he used his big serve to full advantage firing four aces and going up 6-1 before closing out 7-2.

Cilic kept the pressure up, breaking the Frenchman in the fourth set, surging in front 5-0 and then serving out for the match.

"The fourth set was incredible serving, it can't get be better I guess," said Cilic. "I didn't lose too much energy today, so it's good news for me. Going to try and keep my streak going for a couple more matches."

On Saturday, Andy Murray and Simona Halep strolled into the fourth round. Third seed Murray made it to the fourth round with a clinical 6-3, 6-2, 7-5 victory against Brazilian Thomaz Bellucci.

Swiss Stan Wawrinka took the quick route into the last 16, by breezing past Belgian Ruben Bemelmans 6-3, 7-6 (7-5), 6-4.

Richard Gasquet also wasted little time, the 12th seeded Frenchman romping to a 6-4, 6-3, 6-1 win over a drained Australian Bernard Tomic, who was coming off a gruelling five-set battle with compatriot Lleyton Hewitt.

Halep worked the night shift for the first time at this Slam and found it to her liking as she steamrolled past American Shelby Rogers 6-2, 6-3 in 67 minutes.

It was a mixed day for German contenders as Victoria Azarenka of Belarus beat 11th seed Angelique Kerber 7-5, 2-6, 6-4 though Sabine Lisicki advanced beating Czech Barbora Strycova 6-4, 4-6, 7-5.

Donald Young, once hailed as the next great American tennis player, is finally showing that potential at 26 to an excited hometown audience fighting back from two sets down to claim a 4-6, 0-6, 7-6 (7-3), 6-2, 6-4 victory over 22nd seed Viktor Troicki of Serbia.

Young has had a workout this week, escaping another two-sets deficit in his opening match to beat French 11th seed Gilles Simon 2-6, 4-6, 6-4, 6-4, 6-4 then beating Britain's Aljaz Bedene in four sets in the second round.

Murray, who won his first major at the 2012 US Open a year before winning Wimbledon, had fought back from two sets down to beat France's Adrian Mannarino in the second round, after needing four sets to beat Australian Nick Kyrgios in his opening match.

A routine win on a cool, comfortable night after a week of stifling heat gave Murray, who has also battled a head cold, the last berth in the fourth round and should prime the Scotsman for the pressures of the later stages at the year's last Grand Slam.

"Conditions were so much nicer to play in on Saturday," the world No. 3 said. "Like after long rallies, you weren't really struggling for breath as much.

"The first couple rounds, it really doesn't get much harder than that. Maybe it will get bad again, but they're some of the toughest conditions you'll play in during the year. To get through those matches, especially the second one, was important."