Oozing the confidence of a Grand Slam champion, Switzerland's Roger Federer opened his U.S. Open campaign with a win over a cramping Jose Acasuso.

The Argentine retired from the first round match while trailing the Wimbledon champion 5-7, 6-3, 6-3, 2-0.

"I was already winning at that stage," Federer said, heading off suggestions he had been fortunate.

Women's ninth seed Daniela Hantuchova survived a late scare against Russia's Julia Vakulenko.

The skinny Slovak ousted the Russian 6-0, 7-6 in an edgy match on Armstrong stadium court.

"I am just so glad I could get through that match," she smiled as she walked off court. "I lost a little bit my rhythm in the second set so I am definitely relieved."

It was not a victory without drama.

At one point the sometimes emotionally frail Hantuchova almost burst into tears when she missed a match point in the 10th game of the second set.

But she quickly pulled herself together and despite some tenacious and insistent moon-balling by Vakulenko, Hantuchova prevailed in the tiebreak.

She will next meet Thai Tamarine Tanasugarn. Tamarine ousted 18th-seeded Swiss Patty Schnyder 6-4, 6-3.

Hantuchova was joined in round three by France's Amelie Mauresmo. The fifth seed trounced fellow Frenchwoman Stephanie Cohen-Aloro 6-2, 6-2.

"I thought I played a good match, you know?" she said. "I think every part of my game was working very well.

After skipping Wimbledon with a rib injury, Mauresmo said she was finally healthy and looking forward to a successful run at Flushing Meadows.

"I am feeling more and more competitive out there, that's what is important. No more problems with my back or whatever... so far so good," she said.

Federer swiftly recovered from a stuttering start to impose himself on Acasuso.

Federer would have expected only minimal resistance from the 75th ranked Acasuso. The claycourter had won just one match since April and suffered first-round exits in six of seven previous events.

But the Argentine offered plenty of fight on his way to taking the opening set.

However, there was never a hint of panic from the stylish Federer. The Swiss serve and volleyer calmly settled into the match and slowly took control.

His victim in the Wimbledon final last month, Mark Philippoussis, was also in form. He beat Serb Janko Tipsarevic 6-2, 7-6, 6-4.

"The first one is always the toughest," he said. "There were a lot of nerves."