SINGAPORE - World No. 1 Angelique Kerber was made to sweat for an opening victory on Sunday night at the BNP Paribas WTA Finals Singapore presented by SC Global, being taken the distance before she tamed Slovakia's Dominika Cibulkova.

The German won 7-6 (7-5), 2-6, 6-3 to win her first match in the Red Group.

Against her eighth-ranked opponent who did not hesitate in some bold shot-making, Kerber had to scramble for a strong third set after a weak second set marred by unforced errors.

Said Kerber, this year's top performer with titles at the Australian Open and US Open: "(Dominika) is such a tough opponent and I knew I had to play my best tennis today. I'm really happy that I won in the end.

"I was trying to stay positive, be aggressive and go for it. I had to focus on getting my first serves in."

Kerber, competing at the Finals for the fourth time, is hoping to make it out of the round-robin stage for the first time.

The players in the Red Group will have a day off on Monday while those in the White Group - defending champion Agnieszka Radwanska of Poland, Garbine Muguruza of Spain, Karolina Pliskova of the Czech Republic and Svetlana Kuznetsova of Russia - take the court.