The Belgian 27-year-old, who triumphed in New York last year at what was only her third tournament after coming out of retirement, overcame the American 4-6 7-6 (7/2) 6-4 in two hours and 23 minutes on the Arthur Ashe court.
“I just tried to make the points and whenever I felt I had the opportunity to step up and accelerate a little bit, I tried to keep the pressure on her,” said Clijsters after sealing her 20th-straight victory at Flushing Meadows.
“It was a great match to play. The conditions weren’t easy but I think we played some high level tennis. It was a fun night.”
Clijsters will now face No7 seed Zvonareva after the Russian 26-year-old upset top seed Caroline Wozniacki to win 6-4 6-3 in under an hour-and-a-half.
“It was a tough match, Caroline was here in the finals last year and she’s a great player,” said Zvonareva, who reached the Wimbledon final in July. “It was very difficult for both of us with the wind but I think I was patient and aggressive like in the previous matches.
“It was a great experience for me at Wimbledon but I think it’s in the past, I’m trying to look forward at the moment and am just enjoying this day, my win today. I will think about the match later.”
Beaten Wozniacki acknowledged the Russian’s tenacious performance: “She played a really good game. She was not missing a lot. She was going for her shots, most things were going in. I had chances and I made some mistakes today that I usually don’t do.
“It was a tough day for me in the office,” continued the Dane. “That’s the way tennis is sometimes. I definitely was playing great tennis up to the tournament and in the tournament. Even today I had periods where I was playing really well.
“Of course I really don’t like losing, but I just need to learn from this. I made it to the semi-finals of the US Open and when I look back on this tournament I can be proud of what I’ve achieved.”
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BIOGRAPHY: Cesc Fabregas