ISTANBUL, Oct 23: World number one Serena Williams showed her determination to defend her WTA Championships title by sweeping to a 6-3, 6-1 win over Angelique Kerber at the season-ending event on Tuesday.

The 32-year-old American broke early in each set and was too strong for the German, hitting 31 winners.

Kerber qualified for the eight-strong tournament only because Maria Sharapova pulled out.

Serena has been drawn with Agnieszka Radwanska, Petra Kvitova and Kerber in the red group at Istanbul’s Sinan Erdem dome.

Czech Kvitova battled to a 6-4, 6-4 victory over Agnieszka Radwanska of Poland. Results (prefix number denotes seeding):

Red Group: 5-Petra Kvitova (Czech Republic) bt 3-Agnieszka Radwanska (Poland) 6-4, 6-4; 1-Serena Williams (US) bt 8-Angelique Kerber (Germany) 6-3, 6-1.—Reuters