Serena Williams and Kerber qualify for Tour finals

Serena Williams and Angelique Kerber, battling it out for the world number one ranking, are the first two women to qualify for the season-ending WTA Tour Finals in Singapore, the WTA said on Monday. World number one Williams, who leads Kerber by 190 ranking points, has won the title five times but missed last year's event through injury. Kerber, who won her first grand slam title at the Australian Open in January and who reached the final at Wimbledon, will be making her fourth appearance in the