Samantha Stosur of Australia serves to Maria Kirilenko of Russia during their match at the US Open tennis tournament in New York, Sept 4, 2011. [Photo/Agencies]

NEW YORK - Australia's Sam Stosur has emerged as the ironwoman of this year's US Open after the ninth seed enhanced her reputation as one of the toughest players in the game with a second record-breaking win in a row.

On Friday, she won the longest women's match ever played at the tournament, a three-and-a-quarter-hour slugfest against Russia's Nadia Petrova.

Then on Sunday, Stosur was at it again, this time playing the longest women's tiebreak at any grand slam, against another Russian, Maria Kirilenko.

Stosur lost the 32-point tiebreaker 17-15 but went on to take the match 6-2 6-7 6-3. "Obviously I knew it was pretty long but I lost track of the score," Stosur told reporters.

"I didn't know at one point if I was serving or receiving or when we should be changing ends, what was going on.

"So I've got another record here at the US Open, which is cool. It was a shame I didn't win it (the tiebreak)."

During the tiebreaker, Stosur squandered five match points, including three shots from Kirilenko that were called out but overturned by successful challenges.

"I guess that's the great thing about Hawk Eye. It's always a fair match and you don't get ripped off if you've got it," Stosur added.

The Australian made the final of the French Open last year but is still chasing her first grand slam title.

The hardcourts at the US Open suit her big serving game and she has developed a strong following with the New York crowds because of her never-day-die approach.

A year ago, she saved four match points in her fourth-round match with Elena Dementieva. The match finished at 1.35 a., the latest finish for a women's match at the US Open.

"I'm really proud of myself for getting through these two matches," she said. "I haven't always been known for my competitiveness out there, to really fight hard, but for it to come out back to back days, it's definitely very rewarding. I know now I can do it."

Her next opponent is another Russian, second seed Vera Zvonareva.