Wozniacki won four consecutive games in the first set and later took advantage of an ailing Cibulkova, who was playing with her right hip bandaged. She took a medical timeout while trailing 2-1 in the third set.
The third-seeded Wozniacki struggled with her serve in the second set as both players traded breaks four times. The Dane was serving for the match twice in the set but was broken at love on both occasions. Cibulkova then had her left ankle treated.
``The difference at the end was that I just could keep my highest level up to the end,'' Wozniacki said, ``and I managed to win most of the important points, especially at the beginning of the third set.''
The 11th-ranked Wozniacki, who finished the last two seasons at No. 1 on the WTA rankings, has a chance to overtake Marion Bartoli of France at No. 10 by the end of the season if she wins titles in Moscow and at the season-ending Tournament of Champions on Oct. 30.
In her seventh semifinal this season, Wozniacki will play either Maria Kirilenko of Russia or Sofia Andersson of Sweden.
In the men's tournament, Malek Jaziri became the first Tunisian to reach an ATP semifinals when he beat Lukas Rosol of the Czech Republic 7-6 (5), 6-3.