Simona Halep will take over the top ranking by reaching the final in the China Open. Halep beat Jelena Ostapenko 6-2, 6-4 to become the first Romanian No. 1 when the rankings are released Monday.
Halep could have reached the No. 1 ranking earlier this year but was upset in the French Open final by Ostapenko in their first career meeting.
''Of course it's the best moment in my life, and I want just to keep it,'' Halep said in Beijing. ''And I have few more dreams in my career. I tell you one, only one. To win a Grand Slam.''
Halep only had to reach the final this week - and not lose to Elina Svitolina of Ukraine in the final - to knock Garbine Muguruza from the top spot. Muguruza retired during her opening match on Monday because of a cold.
Svitolina was ousted by unseeded Caroline Garcia of France in a marathon quarterfinal encounter.
Halep will play the winner of the semifinal between Garcia and Petra Kvitova of the Czech Republic. The Romanian will be looking for her second title of the year after winning in Madrid.
Ostapenko entered the semifinal without the loss of a set during the week. But Halep dominated the first set, breaking Ostapenko's serve in the first game at love. She cemented her lead with another break in the seventh game for a 5-2 lead to serve out the set.
In the second set, Halep surrendered a 3-2 lead with a service break in the sixth game, but went on to break serve again in the ninth game. At 40-0 in the final game, Halep won with a clean forehand winner down the line.