NEW YORK (Reuters) - Lleyton Hewitt extended his impressive summer form with a straight sets demolition of Amer Delic in first-round action at the US Open yesterday.

The former world number one smacked 31 winners and won 95 percent of the points on his first serve during an easy 6-2 6-4 6-2 triumph over the shell-shocked American.

"Delic is the kind of guy, you give him the half opportunity he's going to take it, come to the net, put pressure on you," said Hewitt, the 2001 Open champion.

"He doesn't have the best passing shots out there. So it was a matter of me mixing it up when I had the opportunity, come in on his backhand, make him press."

While most of the top seeds advanced, there was one notable casualty on the second day of the year's final grand slam.

Ninth seed Daniela Hantuchova was sent packing by Ukrainian Julia Vakulenko 6-4 3-6 6-1, the 24-year-old Russian's earliest exit at Flushing Meadows since her 2001 debut.

Elsewhere, 2004 Open champion Svetlana Kuznetsova whipped Czech Klara Zakopalova 6-2 6-3 while 1997 winner Martina Hingis bounced Frenchwoman Mathilde Johansson 6-0 6-3.

Other winners included sixth seed Anna Chakvetadze, number 11 seed Patty Schnyder, 13th seed Nicole Vaidisova and number 26 Sania Mirza.

On the men's side, Serbian third seed Novak Djokovic looked like a legitimate threat to claim his first grand slam with a 6-2 6-1 6-3 victory over Dutchman Robin Haase.

American James Blake, seeded sixth, needed two hours and 41 minutes to oust compatriot Michael Russell 7-6 6-3 7-6 and set up a second-round match against Frenchman Fabrice Santoro.

Delic said the 26-year-old Hewitt may be overlooked as an Open contender because of the grand slam success of Roger Federer and Rafael Nadal.

"I think he gets lost in the shadow behind guys like Roger and Nadal right now because obviously they're the big hype," said Delic, ranked 71st. "But every time he steps on the court you just can't take him as an underdog. The guy does not give you absolutely anything."

Hewitt agreed with Delic, saying it has been tough trying to grab the spotlight with Federer and Nadal dominating the landscape.

"They've been the two dominant players in the slams over the last four or five years," said the Australian, who reached the quarter-finals and semi-finals in successive Masters Series events earlier this month.

"No one really has had a chance to win any of the other slams basically. That's what my goal is."

Sixteenth seed Hingis committed only eight unforced errors in her one-hour victory over Johansson. The 26-year-old Swiss was at her best at the right times, converting all four break opportunities.

The five-times grand slam champion said the two weeks she took off prior to the Open helped her "get the hunger and get the spirit back.

"I have nothing to lose, I feel like I can only win at this tournament, only get better."