Feb 16 Serena Williams faces the player she will replace next week as world number one, Victoria Azarenka, in the final of the Qatar Open after overcoming Maria Sharapova 6-3 6-2 in Doha on Saturday.
Top seed and defending champion Azarenka defeated Poland's Agnieszka Radwanska 6-3 6-3 in the other semi-final.
It was the 10th time in succession Williams, who at 31 will become the oldest women to hold top spot since computer rankings began in 1985, had beaten her Russian opponent.
"Maria always plays really well and is so consistent but I'm trying to be consistent as well," Williams told the WTA website (www.wtatennis.com).
The 15-times grand slam winner will officially take over as number one when the rankings are released on Monday.
Asked whether in her early days the American wondered if she might still be playing at 31, Williams replied: "I have nothing else to do. I'm still pretty good at tennis so why not? I'd just rather not sit at home all day.
"It's kinda fun. I love playing. I love winning."
Williams has a healthy career lead over Azarenka, having beaten the 23-year-old Belarussian in 11 of their 12 previous meetings, the only defeat coming in Miami in 2009.
"I just have to be consistent and really focused on my own game," said Azarenka who retained the Australian Open title last month.
"We all know she has a great serve. She's really aggressive and really consistent. So for me it's important to just focus on myself and execute my game." (Writing by Alison Wildey in London, editing by Tony Jimenez)