Justin Henin-Hardenne defied the laws of nature for 81 magical minutes on Saturday to bring world number one Kim Clijsters to her knees and capture her first US Open crown.

That she was even able to compete in the final of the last grand slam of the year was a minor miracle in itself; playing near-perfect tennis to win 7-5, 6-1 is the stuff of folklore.

It was a performance that won the 21-year-old a cool $1 million but, to Henin-Hardenne, it was priceless.

"It is such a great feeling. I am so happy right now ... two grand slams in the same year I can't believe it," she said.

"I tell you, I am the happiest woman in the world right now. It has been a terrific two weeks."

Never mind that a representative of sponsor JP Morgan Chase blundered by asking the crowd to congratulate 'Christine' Henin-Hardenne before the trophy presentation.

This victory puts her name up there with some of the sport's greatest comeback artists and installs her as world number two on Monday -- still behind Clijsters but closing fast.

It was an incredible achievement considering just hours earlier she had lain exhausted on a bed in the Flushing Meadows infirmary with an intravenous drip in her arm, suffering cramps and dehydration.

While Clijsters had been tucked up in bed on Friday night, Henin-Hardenne had been locked in battle with a tigerish Jennifer Capriati in a three-hour semi-final stretching into the early hours of the day of the final.

Such was the state of Henin-Hardenne as she limped off court to a standing ovation that there were very real fears she would not be able to take her place on court for the Super Saturday showdown.

But Henin-Hardenne is hewn from tougher stuff.

"I went to sleep at 3.45am and then I was awake at 8.30am," she said of her preparation.

"Tried to sleep a little bit more until 11.30am but it was very hard because the match was still in my mind.

"But I think the trainers and the doctors did a great job. I believed in my chances. I went on the court to win the match and it worked pretty good."

The determination she showed comes as no surprise to anyone who knows her, for her sublime God-given talent is backed by a steely temperament.

It is a temperament that steered her to beat Clijsters in the final of the French Open earlier this year and one which on Saturday made Clijsters' world number one ranking appear little more than an arithmetical error.

Clijsters had looked unstoppable throughout the tournament. She had not lost a set on her way to the final. In fact, she had not lost more than six games in any match over the fortnight.

But under the floodlights on Arthur Ashe Stadium Court, Henin-Hardenne made her look clumsy and inept.

In fairness, though, there are few players in the history of the sport who could share a spotlight with Henin-Hardenne when she is on form.

On Saturday, she was on fire.

The Henin-Hardenne backhand has always been a thing of beauty. From the moment she stepped onto centre court it was jaw-dropping.

Rolling the ball crosscourt or down the line with equal grace and power, Henin-Hardenne raced into a 3-0 lead.

There was little sign of the exhaustion that had all-but scuppered her chances earlier in the day as she scampered around the court.

The 20-year-old Clijsters, who despite her ranking is gaining a reputation for folding in the big matches, scrapped back and even managed to overhaul her opponent for a 5-4 lead.

But Henin-Hardenne reeled off three straight games to clinch the opener in 51 minutes when Clijsters ploughed a forehand into the net for her 30th unforced error.

It was the first set dropped by Clijsters in the entire tournament and the spell was well and truly broken.

Henin-Hardenne started the second set the way she began the first with a pair of breaks on way to another 3-0 lead.

This time she didn't offer Clijsters any chance to get back into the match, holding serve to go 4-0.

Clijsters finally stopped the skid by holding serve at 4-1 but the road back was too far, Henin-Hardenne finishing off her beleaguered compatriot with another break.

"That just shows how good an athlete she is," Clijsters said. "I was disappointed. I felt the first six matches coming into the final I played much better."

"But on the other hand I played an opponent who was the best player out there today and the best player all tournament. Although it is very disappointing, I felt that today Justine was just too strong and dealt with it very well."

"So far my whole season has been really good so I don't want, by losing this match, for it to overshadow all I've done this season," Clijsters said.