Serena Williams retained the No. 1 world ranking by beating her sister Venus 6-4, 3-6, 6-3 in the semifinals of the Sony Ericsson Open on Thursday.
The match was the 20th meeting between the sisters and each has won 10 times.
Serena needed to reach the final to retain the top ranking she has held since February 2. Otherwise, she would have been supplanted next week by No. 2-ranked Dinara Safina of Russia.
"I'm excited," Serena said. "I was thinking I'd love to remain No. 1. I think I was more happy about that than winning the match."
Serena's opponent today will be 19-year-old Victoria Azarenka of Belarus, who beat 2006 champion Svetlana Kuznetsova 6-3, 2-6, 7-5.
Azarenka became ill with a stomach complaint before losing a fourth-round match against Williams at the Australian Open in January.
still here to win
Serena jumped to a 4-1 lead in the final set against her older sister and broke serve for the sixth time in the final game. When she closed out her victory, she hopped in delight, raised a fist and shouted "Yes!" She then met her sister at the net with a handshake and slap on the back.
"Even though she's my sister, I'm still here to win," Venus said. "I can't give anyone anything. So I'm disappointed that I lost tonight, whether or not she kept the ranking or not."
Top-ranked Rafael Nadal lost in the men's quarter-finals to 20-year-old Argentine Juan Martin del Potro 6-4, 3-6, 7-6 (3). The upset delighted a partisan crowd that included many transplants from Argentina.
Del Potro had lost all nine sets in their four previous matches, but he was buoyed by a homecourt advantage, with many Argentines in the crowd singing "Del-Po" between points.
"Wonderful for the crowd," top-ranked Nadal said. "Terrible for me."
Del Potro showed patience in long rallies and used his looping forehand to keep Nadal deep as their three-hour match built to a dramatic finish.
"I beat him with my mind and with my game," del Potro said. "When we played long points, I was dominating every time."
Nadal was up two breaks in the final set at three love, but del Potro climbed back into the match by winning 12 of the next 14 points.