All women's semi-finalists in line for No. 1 rank

New York: Women's semi-finals day will have added spice to it at the US Open on Friday with the carrot of the No.1 ranking looming large over the four remaining protagonists.

American Serena Williams, Russians Dinara Safina and Elena Dementieva and Serbian Jelena Jankovic can all replace another Serbian, Ana Ivanovic, at the top of the rankings by winning the title in New York.

Of more immediate concern to all of them will be earning a place in the final, with Serena chasing her ninth Grand Slam title and the other three closing on their first.

Having defeated her sister Venus in a high-quality quarter-final, fourth seed Serena is the obvious favourite but she will have her hands full against Safina, the most in-form player on the women's tour.

The Russian sixth seed has reached the final in six of her past seven events, and was runner-up at both the French Open and Olympics.

The 26-year-old Serena, however, has been hard to derail this close to the big prize, having won 11 of her previous 13 Grand Slam semi-finals, and Safina admitted beating her will be a tough task.

"First of all, she is a great fighter and she's very dominant on the court," Safina, 22, said about Serena.

"She likes to put pressure on the players, so that's why it makes her a very tough opponent."

The quarter-final meeting between the Williams sisters could easily have been a final, as it was at Wimbledon this year, and Serena said she would have to focus against Safina.

"I feel like I should have a trophy now," she said after Wednesday's thrilling quarter-final.

"Unfortunately I don't, and I have to go to the next round. I don't want to go out in the next round, especially not after that."

Serena has won three of four matches against the Russian, but Safina prevailed in their last meeting, on clay in the quarter-finals this season in Berlin.

In the other semi-final, Olympic champion and fifth seed Dementieva takes on second seed Jankovic, who is looking to reach her first Grand Slam final.

Dementieva, the Open runner-up in 2004, has yet to drop a set in the tournament and has spent three hours less on court than Jankovic, who was made to fight much harder than expected in the early stages.

"I'm very excited to be in the semis, but I'm sure I need to improve my game and play a better match if I want to go to the final," Dementieva, 26, said after her quarter-final demolition of Swiss 15th seed Patty Schnyder.

Jankovic leads her personal series against Dementieva 4-3, though she also lost to her Open semi-final opponent in this year's Berlin quarters.

After an impressive win over Austrian Sybille Bammer in the previous round, Jankovic said she was beginning to feel good.

"In the beginning of the tournament, I was really not feeling that great, because I wasn't able to practice," Jankovic, 23, said.

"I was injured at the Olympics and throughout most of the year. So of course I couldn't expect for myself to be at the top of my game and in top shape. "But I'm willing to work hard and trying to get better every day, and I'm really happy how I'm doing, how I'm progressing, how I'm developing."