Serena: I'll be No.1 again

Johannesburg - World number three Serena Willams on Saturday vowed to top the WTA rankings again, after finishing a year that saw her make a remarkable comeback from a potentially life-threatening condition.

"I've been number one and believe me I'll be number one again," Williams told a news conference in Johannesburg during an Africa tour with her sister Venus to promote the sport among young girls.

Williams finished 1195 points behind top-ranked Victoria Azarenka of Belarus on the WTA rankings, and 645 adrift of number two Maria Sharapova of Russia.

The rankings drew some criticism as Williams beat Sharapova in the WTA Championship in Istanbul last Sunday, and won two Grand Slams this year as well as Olympic gold in the singles and doubles in London.

But she was little concerned about the rankings, she said.

"I'm not really thinking of it so much. I'm focusing on the Grand Slams."

"I had a slow start and that really affected my ranking."

Williams' stellar performance this year followed a lengthy spell on the sidelines due to a potentially life-threatening blood clot on the lungs.

She is visiting South Africa with sister Venus to give tennis training in iconic township Soweto in Johannesburg and promote the sport under African girls after a similar trip in Nigeria earlier this week.

The sisters will play an exhibition match against each other on Sunday.