(CNN) -- Victoria Azarenka reached the semifinals of the U.S. Open for the first time after battling past defending champion Samantha Stosur in three sets Tuesday.
The world No. 1 lived up to her status with a 6-1 4-6 7-6 (7-5) victory over the seventh seed from Australia in a match disrupted by a 75-minute rain delay.
"We both showed some excellent tennis," said Azarenka, who has the best record on hard courts this season with a 30-2 winning margin in WTA Tour events.
"You could feel the pressure all the time. We really both gave it all. We fought really hard, making each other run like crazy."
She will play either French 11th seed Marion Bartoli or Maria Sharapova of Russia, who started playing the second quarterfinal before rain ended the rest of Tuesday's schedule.
"To be in the semifinals of the U.S. Open for the first time is incredible. I don't want to stop. I want it bad. I'm going to do absolutely everything I can here," said Azarenka, who had beaten Stosur in straight sets in their previous six meetings.
"She really pushed me to dig deep. She kept coming back really strong and keeping me back, and I wasn't getting as many opportunities -- I just kept telling myself, 'Don't be a chicken, come on, just go, go for your shots.' "
Azarenka was two breaks ahead in the first set when the showers hit Flushing Meadows, but did not take long to close it out when the players returned.
But Stosur, who sensationally beat Serena Williams in last year's final, was not going to relinquish her crown easily and gained an early break in the second set.
Belarus star Azarenka broke back immediately, but dropped her service gain to trail 4-3 and could not recover. It was the first set she had lost in the final grand slam of the season.
The final set saw Azarenka twice lead after breaks, but with tension mounting Stosur twice retrieved the breaks to set up a tiebreaker.
Again Azarenka pulled ahead to a 4-0 lead, but showing signs of nerves she gave up the advantage as the champion leveled at 5 points each.
But a clever drop volley on the next point set up Azarenka for match point and she was soon celebrating victory after nearly two and a half hours of quality tennis as Stosur hit a return wide.
Third seed Sharapova will need to show the resilience she displayed in her previous match against Nadia Petrova if she is to progress to the semifinals in New York since she won the title in 2006.
The French Open champion dropped her serve twice against Bartoli to trail 4-0 when play was halted.
However, she has won 23 of 24 matches that have gone to three sets since the start of 2011, including 11 this year.
Bartoli, who beat former Wimbledon champion Petra Kvitova in the previous round, has never got this far in the tournament in 10 previous attempts, with her best showing having been reaching the fourth round in 2007 and 2008.
Wednesday's remaining last-eight clashes will see Wimbledon and Olympic champion Williams take on fellow former world No.1 Ana Ivanovic of Serbia and an all-Italian clash between Sara Errani and Roberta Vinci.
French Open singles finalist Errani will become the world's top-ranked doubles player on Monday, while her partner Vinci will be the new No. 2 after they reached the semifinals with victory against Germany's Julia Gorges and Czech Kveta Peschke.
They will replace former joint No. 1s Lizel Huber and Lisa Raymond of the U.S. -- whose title defense ended in round three.
Errani and Vinci are battling for the honor of being the first player from their country to reach a singles semifinal at a grand slam other than the French Open.