NEW YORK, Sept. 8 -- World No. 1 Caroline Wozniacki and three-time champion Serena Williams both cruised into the semifinals of US Open on Thursday and had to face off for a final slot.
Last year's runner-up Vera Zvonareva, No. 2 seed, succumbed to Aussie Samantha Stosur in straight sets of 6-3, 6-3 in a quarterfinal.
The 2009 US Open runner-up Wozniacki got past 10th-seeded German Andrea Petkovic 6-1, 7-6 (5) in 1 hour and 40 minutes in another quarterfinal, including a hard-fought 73-minute second set.
The top-seeded Dane broke Petkovic six times, compared to three breaks for the German, who reached the quarterfinals at three of the four Grand Slam events this year, her best-ever one on the WTA circuit.
The 21-year-old Wozniacki will challenge Williams for a third time, all on hardcourts, seeking a first ever win. The two stars haven't met since the 2009 season.
The 28th-seeded Williams overpowered 17th-seeded Russian Anastasia Pavlyuchenkova 7-5, 6-1 with her seventh ace of the play to end the contest, advancing into semifinal hitting 26 winners.
The powerful American broke the young Russian six times and Pavlyuchenkova piled up 31 unforced errors en route to the predictable defeat.
"I think Caroline is a very consistent player," Williams said. "I think both consistent on the court and then consistent in playing tournaments and doing well and winning tournaments as well as going really far in tournaments. That's pretty much what it takes to be the best."
The 29-year-old Williams is a 13-time major titlist, including a trio of US Open victories. She also posted a runner-up finish to her older sister Venus here in Flushing Meadow 10 years ago.
Serena is currently riding a 17-match overall winning streak, all on hardcourts, which includes titles in Stanford and Toronto.
Ninth-seeded Stosur beat Zvonareva for an eighth straight time, as the Aussie posted a comprehensive 6-3, 6-3 victory in 67 minutes.
Stosur fired 25 winners, compared to only nine for the Russian. The Australian converted three of four break points, while Zvonareva was unable to get even a break point.
"When you're playing well, it just kind of flows," said Stosur. "You step up to the line and you play the next point and the next one and the next one. Happy to close it out in straight sets."
Stosur was last year's French Open runner-up, while Zvonareva lost in last year's US Open and Wimbledon finals.
The 27-year-old Stosur will now appear in her third career Grand Slam semifinal and her first-ever US Open semi.
She'll play against upstart 92nd-ranked German Angelique Kerber on Saturday.
The 23-year-old left-handed Kerber will appear in her first career Grand Slam semifinal after upending 26th-seeded Italian Flavia Pennetta 6-4, 4-6, 6-3.