Jelena Jankovic fell short in her quest to become world number one after the top seed lost to Dinara Safina in the semi-finals of the East West Bank Classic on Saturday.

The Serbian went down 7-6 (7/3) 6-1 to the fourth-seeded Safina, who will now face number 10 seed Flavia Penetta in the final in Los Angeles.

Ranked second in the world, Jankovic was aiming to overtake compatriot Ana Ivanovic and become the 18th player in history to hold down the top spot in the WTA rankings despite never having reached a Grand Slam final.

However, she could not overcome Safina, who has been one of the hottest players on the WTA Tour recently and improved her record

to 21 wins against just three losses since the start of May, a run that included a title in Berlin and a surprise appearance in the final of the French Open, where she lost out to Ivanovic.

The 22-year-old Russian was also a finalist at 's-Hertogenbosch just prior to Wimbledon, where she suffered a third-round loss.

Safina's recent run is even more remarkable considering that eight of those 21 wins have come against top-10 players.

Earlier, Italian Penetta booked her place in the final after a 3-6 6-2 7-5 victory over wildcard Bethanie Mattek.

The 23-year-old American was bidding to reach her first WTA final after an impressive run this week but after taking the first set, the world number 59 found the challenge of Penetta too strong to overcome.