World number one Rafael Nadal rolled into the fourth round of the US Open, winning the final 11 games to answer a fightback while serving notice he could take his first Flushing Meadows title.

The Wimbledon and French Open champion raised his game when challenged to defeat Serbia's 71st-ranked Viktor Troicki 6-4, 6-3, 6-0, giving the Spaniard his 41st triumph in his past 42 starts on Saturday.

“I have started playing better,” Nadal said.

“I served very well. I have more confidence and I hope to continue to improve my tennis. I know I have to keep improving my tennis if I want to win,” he added.

Nadal can match his best US Open showing to date by winning his next match over Sam Querrey, the 55th-ranked American who ousted Croatian 14th seed Ivo Karlovic 7-6 (7/5), 7-6 (7/5), 6-2.

Seventh-seeded Venus and fourth-seeded Serena Williams also advanced to the fourth round, the US sisters who met in the Wimbledon final moving one step closer to a quarter-final showdown at the year's last Grand Slam championship.

British sixth seed Andy Murray rallied past Austrian Jurgen Melzer 6-7 (5/7), 4-6, 7-6 (7/5), 6-1, 6-3, booking a date with Swiss 10th seed Stanislas Wawrinka in the round of 16 after battling for three hours and 52 minutes.

France's Gael Monfils pulled off the biggest surprise so far on the men's side by ousting Argentina's seventh-seeded David Nalbandian 6-3, 6-4, 6-2.