Victoria Azarenka of Belarus celebrates after defeating Samantha Stosur of Australia in their women's singles quarterfinals match at the US Open tennis tournament in New York September 4, 2012. [Photo/Agencies]

NEW YORK - The wind was blowing a gale and a dark storm was closing in but that was the least of Victoria Azarenka's problems at the US Open on Tuesday.

Australian Sam Stosur roared back from the brink of defeat three times to steal momentum and put world number one Azarenka in danger of losing a quarter-finals match she had seemed to have under control.

"She really pushed me," said Azarenka, who survived her rain-interrupted ordeal to win 6-1 4-6 7-6. "I think that the quality of tennis was really high. It was tense because it could go either way."

Azarenka had won her previous six matches with Stosur in straight sets and seemed to be on course for a seventh clean sweep when she romped through the first set in just 30 minutes.

Stosur took the second set after the match was suspended for 75 minutes because of a rain delay but Azarenka looked to have tightened her grip when she broke the Australian's serve to lead 3-1 in the third.

Samantha Stosur of Australia waves to the crowd as she leaves following her defeat to Victoria Azarenka of Belarus in their women's singles quarterfinals match at the US Open tennis tournament in New York September 4, 2012.  [Photo/Agencies]

But Stosur, who upset Serena Williams to win her maiden grand slam title at the US Open last year, fought back to level the set and force a deciding tiebreak.

Azarenka raced out to a 4-0 lead but Stosur was not finished yet and Azarenka's nerves were starting to fray. The Belarusian double-faulted and suddenly the pair were locked at 5-5, both two points away from winning and defeat.

"You don't want to know what I kept telling myself. I would have to beep that," Azarenka said. "I kept telling myself, 'don't be a chicken, just go for your shots.'"

That can be easier said than done in the pressure-cooker atmosphere at Arthur Ashe Stadium but Azarenka stayed true to her faith.

She set up her match point with a cleverly disguised dropshot then sealed victory with a perfectly struck forehand that caught the baseline.

"I think everybody prefers to win maybe a little bit easier than this way," she said. "But it definitely gives a lot of boost.

"I enjoy the fight. I enjoy the struggle, that pain that we go through, that incredible moment that you feel relieved after you know you gave it all in every point you had."

The rewards for winning were instant. She booked herself a first semi-final appearance at Flushing Meadows, against either Maria Sharapova or Marion Bartoli, and ensured she would remain world number one regardless of how much further she went.

Her joy and relief was obvious when she broke into an impromptu dance but the Belarusian already has her mind on a greater prize.

Earlier this year, she won the Australian Open to capture her first grand slam title, but rather than satisfy her ambition, it only fuelled it.

"Being in the semi-finals in the U.S. Open is an incredible feeling for me but I definitely don't want to stop," she said.

"I really want it bad. I'm going to do absolutely everything I have, you know, to give it all here."