World No. 1 Victoria Azarenka held off defending champion Samantha Stosur on a rainy Tuesday to secure a berth in the semifinals at the U.S. Open.

The Australian Open champion Azarenka edged out the seventh-seeded Stosur 6-1, 4-6, 7-6 (7-5) at Arthur Ashe Stadium, where rain delayed play for 75 minutes with the Belarusian leading 3-0 in the first set.

Azarenka steamrolled her way though the first set before Stosur fought back in the second.

In the third set, Azarenka went out to a 4-2 lead following a break, but Stosur got the break back and eventually forced the match-deciding tiebreak.

Azarenka set up her first match point in the tiebreak with a backhand drop- shot winner, and converted on it when Stosur sent one final backhand beyond the baseline after 2 hours, 23 minutes of quality tennis.

With the victory over Stosur, Azarenka is guaranteed to remain atop the women's rankings next week.

"She played amazing," Azarenka said. "So much higher, the level was today. Again made me play my best tennis. I was hoping for a few outs, but she kept hitting the lines. I kept saying, 'Miss, miss.' She didn't want to, I guess."

The Minsk native Azarenka is now a perfect 11-0 in three-set matches this year and a flawless 7-0 lifetime overall versus Stosur, having won 14-of-15 sets.

The 23-year-old Azarenka will now appear in her fourth career Grand Slam semifinal and her first at the U.S. Open.

Stosur stunned American great Serena Williams in straight sets in last year's U.S. Open finale and was a French Open runner-up in 2010.

Azarenka will meet the Maria Sharapova-Marion Bartoli winner on Thursday. Azarenka beat the French Open champ Sharapova in the Aussie Open championship match back in January.

The third-seeded Sharapova was trailing the 11th-seeded former Wimbledon runner-up Bartoli 0-4 at Ashe when their match was suspended for the day because of rain. The start of the match was delayed by wet weather for an hour-and-a-half.

The former world No. 1 Sharapova captured her lone U.S. Open title in 2006. The 2012 Aussie Open runner-up captured the French Open in June to complete a coveted career Grand Slam.

Sharapova lost to Williams in last month's Olympic gold-medal match.

The women's quarterfinals are scheduled to conclude Wednesday on the hardcourts at the National Tennis Center, where Sharapova will continue her affair against Bartoli, the fourth-seeded Wimbledon champion and Olympic gold medalist Williams will encounter 12th-seeded fellow former world No. 1 Ana Ivanovic of Serbia, and 10th-seeded French Open runner-up Sara Errani will battle 20th-seeded good friend, fellow Italian and doubles partner Roberta Vinci. Errani and Vinci are into the doubles semifinals in Flushing.

Williams owns 14 major singles titles, including three at the U.S. Open, where she's also a two-time runner-up.