NEW YORK (AP) – Top-seeded Caroline Wozniacki defeated No. 10 Andrea Petkovic 6-1, 7-6 (5) Thursday to set up a semifinal matchup against Serena Williams at the U.S. Open.

Wozniacki let a 5-3 lead slip in the second set and wound up in a tiebreaker, but Petkovic made five unforced errors in the breaker and couldn’t complete the comeback.

Wozniacki, who has been ranked No. 1 for most of the last year, has yet to win a Grand Slam title. She is seeking a spot in her second Grand Slam final, but will have to get past Williams to do it.

The top-seeded player was put out on Court 13 after the court inside Louis Armstrong Stadium was deemed unplayable. Wozniacki followed Andy Roddick onto the outside court, which seats fewer than 600 spectators.

(Copyright 2011 by The Associated Press. All Rights Reserved.)

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