NEW YORK - Top-seeded Victoria Azarenka held off defending champion Sam Stosur on Tuesday in a hard-fought match to advance to the semi-finals of the U.S. Open.

In a match that lasted two hours and 23 minutes, Azarenka was able to prevail over a determined Austrailian star after a tie-breaker third set, 6-1 4-6 7-6 (7-5).

"I have no words," said Azarenka, following the match. "You could feel the pressure.

"We played some great tennis. The level was so high. We both gave it our all."

Both players were strong at the net, but Azarenka was particularly strong at keeping Stosur on the run.

Stosur had the more effective serve, as the No. 7 seed finished with five aces and only won double fault, to go along with a 73 percent first-serve percentage. The 28-year-old also reached 114 miles per hour on her serve.

But Azarenka committed just 24 unforced errors compared to Stosur's 32. The Belarusian won six-of-eight break points.

Azarenka will face the winner of third-seed Maria Sharapova and 11th-seed Marion Bartoli for a spot in Saturday's final.