World No.1 Caroline Wozniacki and her chief rankings rival Petra Kvitova had a demanding three-set introduction to the Sydney International in their first official match of the season on Tuesday.

Wozniacki and Kvitova, tuning up for next week's Australian Open, were on court for more than two hours in warm conditions after beginning their Australian campaigns indoors at last week's Hopman Cup in Perth.

After her two hour and 22 minute match against the 18th-ranked Slovakian Dominika Cibulkova, Wozniacki said her 7-5, 2-6, 6-4 victory had been a tough contest.

Kvitova also had a tough fight against Romania's Alexandra Dulgheru, needing two hours and 18 minutes to defeat the world No. 66 7-5, 3-6, 6-4 at the Ken Rosewall Arena.

“I thought I didn't have that chance, but I never gave up the fight,” said Wozniacki, whose tenure at the top of the women's singles rankings comes despite not yet winning a Grand Slam in 19 attempts.

“I'm happy to be through to the next round here. Definitely that I could fight back from that score is satisfying, but I definitely need to step up my game a little bit in the next round.”

Wozniacki set up a quarterfinal clash against Polish seventh seed Agnieszka Radwanska, who overcame Germany's Andrea Petkovic in straight sets. Wozniacki leads Radwanska 5-1.

Defending champion Li Na also had a difficult time before subduing South African Chanelle Scheepers 2-6, 6-4, 6-1 to set up a quarterfinal with Lucie Safarova of the Czech Republic.

French Open semifinalist Marion Bartoli skated into the quarters with a 6-0, 6-3 win over Australian Jelena Dokic and will play third seed Victoria Azarenka of Belarus in the last eight.

Azarenka accounted for Serbia's Jelena Jankovic 6-4, 6-2.

The results:

At Sydney (APIA International): Women: Second round: Lucie Safarova bt Svetlana Kuznetsova 6-1, 2-0, retd.; Li Na bt Chanelle Scheepers 2-6, 6-4, 6-1; Caroline Wozniacki bt Dominika Cibulkova 7-5, 2-6, 6-4; Daniela Hantuchova bt Francesca Schiavone 7-5, 6-1; Agnieszka Radwanska bt Andrea Petkovic 7-5, 6-4; Petra Kvitova bt Alexandra Dulgheru 7-5, 3-6, 6-4; Marion Bartoli bt Jelena Dokic 6-0, 6-3; Victoria Azarenka bt Jelena Jankovic 6-4, 6-2.

Men: First round: Julien Benneteau bt Andreas Seppi 6-3, 6-4; Fabio Fognini bt Michael Russell 2-6, 6-2, 6-0; Radek Stepanek bt Xavier Malisse 6-7(4), 6-4, 6-4; Alex Bogomolov Jr. bt Robin Haase 6-4, 1-6, 6-4; Marcos Baghdatis bt Dmitry Tursunov 6-4, 6-4; Viktor Troicki bt Lleyton Hewitt 4-6, 6-3, 6-2.

At Auckland (ATP Heineken Open): First round: Adrian Mannarino bt Kevin Anderson 6-3, 6-3; Carlos Berlocq bt Filippo Volandri 6-5 rtd.; Guillermo Garcia-Lopez bt Igor Kunitsyn 2-6, 6-4, 6-2; Philipp Kohlschreiber bt Stephane Bohli 6-4, 4-6, 6-4; Olivier Rochus bt Tobias Kamke 7-5, 6-4; Lukas Rosol bt Albert Ramos 6-2, 6-4; Ryan Harrison bt Sam Querrey 6-4, 6-3; Potito Starace bt Albert Montanes 6-3, 6-2; Benoit Paire bt Juan Carlos Ferrero 6-3, 6-2.

At Hobart (WTA Moorilla Hobart International): Second round: Anna Chakvetadze bt Tsvetana Pironkova 6-3, 6-2; Angelique Kerber bt Sara Errani 6-1, 6-2; Simona Halep bt Irina-Camelia Begu 6-4, 6-2; Sorana Cirstea bt Bethanie Mattek-Sands 2-6, 6-3, 7-5; Yanina Wickmayer bt Casey Dellacqua 6-1, 6-1.

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