Second seed Nadal fired 48 winners and took his year record to 57 wins against just three defeats and his perfect hardcourt form to 19 wins.

He also preserved his record this year at the tournament of not having dropped serve, although he had a rocky start to the evening against the big-hitting Kohlschreiber, who finished with 49 winners but 47 unforced errors.

Nadal certainly had the 29-year-old German under the cosh throughout their last-16 tie, carving out 21 break points, converting five. "It was very tough tonight with the humid conditions, I was sweating too much," said Nadal after three hours and 12 minutes on court. "I had chances in the first set but couldn't take them. I feel lucky to be through as it was physically tough. "But as the match went on I felt more comfortable on my serve." Next up for Nadal is Robredo against whom he has a 6-0 record. "He's playing great and he has had similar circumstances like me in coming back from injury," said Nadal. "He has come back and is having an amazing tournament. He has beaten Federer so he will bring that confidence into the match."

As news of Federer's stunning defeat to Robredo on the neighboring Louis Armstrong Court spread around the Arthur Ashe Stadium, Kohlschreiber sensed his chance of a shock and took the first set on a tie-breaker.

But Nadal eventually broke through for a 4-3 lead in the second set to level up the encounter.

The 27-year-old Spaniard kept up the barrage at the start of the third with Kohlschreiber fending off eight break points in the opening game before Nadal achieved the break in the third game.

He back it up with another break in the ninth as he sighted the quarter-finals. Kohlschreiber, who had only beaten the world number two once in 10 meetings before Monday, was wilting and dumped an easy smash into the net in the first game of the fourth set which would have given him an early break.

Nadal made him pay as he raced away with victory. (AFP)