Relieved Andy Murray hustles into fourth 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 today," the world number three 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."

Murray, whose voice was gravelly earlier in the week from the effects of his cold, was feeling better about his tennis and his health.

"I slept during the day yesterday two or three times," he said. "Today I got up, and I slept again before coming out to the courts. Today I felt much, much better.

"My voice feels like normal again. Still dull obviously, but it feels more normal today and not blocked up or anything."

As for the quality of his tennis, Murray said: "I felt like I played well. In these conditions, it's a bit easier to control the ball. The ball was not bouncing as high. It was a bit sort of flatter.

"It was much slower conditions to serve in. So less aces. The speed of the serve was a bit lower," he added. "But then obviously returning is a little bit easier."

Murray, 28, was pleased with how he is heading into the second week.

"It was a tough, tough start to the tournament for me," he said. "A very testing couple of rounds.

"Today I played a little bit better. I feel better, as well."

Murray will next face 15th-seeded South African Kevin Anderson who beat Austrian Dominic Thiem 6-3 7-6(3) 7-6(3).

French Open champion Stan Wawrinka powered his way to a third successive straight sets win, beating Belgian Ruben Bemelmans 6-3 7-6(5) 6-4.

The aggressive Swiss fifth seed belted 41 winners at Louis Armstrong Stadium to make up for 32 unforced errors against Bemelmans, who was appearing in the third round of a Grand Slam for the first time.

Wawrinka, who won his maiden grand slam at last year's Australian Open, will meet American Donald Young, who battled back to beat Serbian Viktor Troicki after losing the first two sets, for a berth in the quarter-finals. Young eventually came through 4-6 0-6 7-6(3) 6-2 6-4.

In the women's draw, second seeded Simona Halep worked the night shift for the first time at the US Open and found it to her liking as she steamed past American qualifier Shelby Rogers 6-2 6-3 to reach the fourth round at Flushing Meadows.

Halep needed just 67 minutes under the Arthur Ashe Stadium floodlights to complete a dominant display that saw her face a single break point while winning 91 percent of her first serve points.

The 23-year-old Romanian has enjoyed a superb buildup to the year's final grand slam reaching the finals in both Toronto and Cincinnati and carried that form into the US Open, having reached the fourth round without dropping a set.

Halep will next play German 24th seed Sabine Lisicki, who beat Czech Barbora Strycova 6-4 4-6 7-5.

Elsewhere, two-time finalist Victoria Azarenka edged a classic with Germany's Angelique Kerber 7-5 2-6 6-4 to book her spot in the second week.

3-Andy Murray (Britain) beat 30-Thomaz Bellucci (Brazil) 6-3 6-2 7-5

13-John Isner (US) beat Jiri Vesely (Czech Republic) 6-3 6-4 (Vesely retired)

2-Roger Federer (Switzerland) beat 29-Philipp Kohlschreiber (Germany) 6-3 6-4 6-4

6-Tomas Berdych (Czech Republic) beat 31-Guillermo Garcia-Lopez (Spain) 6-7(2) 7-6(7) 6-3 6-3

12-Richard Gasquet (France) beat 24-Bernard Tomic (Australia) 6-4 6-3 6-1

15-Kevin Anderson (South Africa) beat 20-Dominic Thiem (Austria) 6-3 7-6(3) 7-6(3)

5-Stanislas Wawrinka (Switzerland) beat Ruben Bemelmans (Belgium) 6-3 7-6(5) 6-4

Donald Young (US) beat 22-Viktor Troicki (Serbia) 4-6 0-6 7-6(3) 6-2 6-4

2-Simona Halep (Romania) beat Shelby Rogers (US) 6-2 6-3

20-Victoria Azarenka (Belarus) beat 11-Angelique Kerber (Germany) 7-5 2-6 6-4

Varvara Lepchenko (US) beat Mona Barthel (Germany) 1-6 6-3 6-4

26-Flavia Pennetta (Italy) beat Petra Cetkovska (Czech Republic) 1-6 6-1 6-4

22-Samantha Stosur (Australia) beat 16-Sara Errani (Italy) 7-5 2-6 6-1

Johanna Konta (Britain) beat 18-Andrea Petkovic (Germany) 7-6(2) 6-3

5-Petra Kvitova (Czech Republic) beat 32-Anna Karolina Schmiedlova (Slovakia) 6-2 6-1

24-Sabine Lisicki (Germany) beat Barbora Strycova (Czech Republic) 6-4 4-6 7-5