Victoria Azarenka has admitted that it is an "incredible achievement" for her to end the year as the world number one.
The 23-year-old is only the 11th player to finish the season at the top of the rankings since they were established in 1975.
"It's kind of difficult to believe that a little girl from Belarus is on that list, but it's really an incredible achievement," she said.
"When I started to play tennis I had this big picture in my head that I want to be there. Back then it was so far away. It was like pretty much touching the sky."
Azarenka will meet world number two Maria Sharapova on Saturday for a place in Sunday's WTA Championships final.