Serena Williams and Angelique Kerber in 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 Serena, 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 October 23-30 event, reserved for the top eight-ranked players of the year.

“I’m very proud and excited to qualify for the BNP Paribas WTA Finals in Singapore,” said Serena, who will try to break the Open-era record of 22 Grand Slam singles titles she shares with Steffi Graf by winning the US Open which starts next week.

“It is one of the most important events of the year and we all fight to qualify in the top eight,” Germany’s Kerber said in a statement released by the WTA.