Williams beat top-seeded Svetlana Kuznetsova 7-6 (2), 6-1, and Dementieva eliminated fellow Russian Dinara Safina 6-1, 6-0.

"It definitely was not easy," Williams said. "It was a tough first set ... I was playing a really good player and I was enjoying it. It was really cool."

In the men's semifinals, defending champion Nikolay Davydenko beat Janko Tipsarevic of Serbia 7-6 (6), 6-1, and Paul-Henri Mathieu of France downed Michael Berrer of Germany 7-5, 6-3.

Williams put early pressure on the No. 2-ranked Kuznetsova, breaking her in the third game of the first set. But Kuznetsova leveled at 4-4 after Williams netted an easy forehand on the third break point.

Williams dominated the tiebreaker, going up 3-0 and 6-1 before clinching the first set.

The No. 7-ranked Williams then broke Kuznetsova in the second and fifth games of the second set.

"The match was decided in the first set," said Kuznetsova, the 2004 U.S. Open winner who was playing in her 300th professional match. "I failed to play right on several key points and allowed Serena to play too comfortably."

Williams has not dropped a set on the way to her third final this season. The eight-time Grand Slam champion is playing in Moscow for the first time in a decade. In 1997 the then 16-year-old qualified and lost in the first round when she was ranked 448th.

Dementieva, the 2001 and 2004 runner-up, had little trouble against an erratic Safina. After trading breaks early in the first set, Dementieva won eleven consecutive games.

"I'm not the favorite in tomorrow's final since I have never managed to beat Serena," she said. "But for me it's a good chance for revenge."

In their first matchup, Tipsarevic, ranked 68th, saved three break points against top-seeded Davydenko in the 11th game of the first set to force a tiebreaker. But the fourth-ranked Russian had little trouble in the second set, winning five consecutive games.

"It was very tough to take the first set," Davydenko said. "I made too many mistakes."