Williams got off to a shaky start against Safina, the younger sister of 2000 US Open men's champion Marat Safin.

Broken in her first service game, Williams fell behind 2-0, but she won seven of the next eight games, eventually doing a much better job than Safina of dealing with wind that gusted at over 20 mph.

Safina wound up with 41 unforced errors, and she repeatedly rolled her eyes or shook her head or shouted at herself in English or Russian, much the way her brother does. In the second set, Safina hit her fifth double-fault of the match and yelled, "I hate the wind!" Two points after that, Safina pushed a backhand long and Williams broke to lead 2-1 in the second set.

The whipping air played havoc with serve tosses, the women combined for 11 double-faults, and all manner of other strokes. The US flag above the video board at one end of Arthur Ashe Stadium rippled so loudly that Safina turned to glare at it before one serve.

"I thought, 'OK, if it's so windy, then I'm not going to go for so many winners," said Williams, who didn't produce her first winning forehand until the match was 30 minutes old.

It's Williams' first US Open final since she beat older sister Venus six years ago. This time, she dispatched Venus in the quarterfinals.

"Overall, she's, I think, the strongest player on the tour, together with her sister," said second-seeded Jelena Jankovic, who will meet the fourth-seeded Williams in the final. "Nobody has the power that they have. We cannot compare."

Like Williams, Jankovic began poorly in the semi-finals before eliminating Olympic gold medalist Elena Dementieva 6-4, 6-4. It will be Williams' 12th Grand Slam final, and Jankovic's first, and in addition to the silver trophy at stake, the winner will rise to No 1 in the rankings next week.

The final is scheduled for Saturday night, but forecasts calling for rain much of the day prompted tournament organisers to announce contingency plans that could include postponing the match until Sunday.

"I'm going to try my best and that's all I care about," Jankovic said, "even if it's tomorrow or next day or in a week."

She lost eight of the first nine points and fell behind 2-0 and 4-2. But as Dementieva became more tentative and more erratic, Jankovic reeled off five consecutive games to claim the first set and a 1-0 edge in the second.

Jankovic also trailed by a break at 3-2 in the second set, before coming back again. She got plenty of help, 42 of the 66 points Jankovic won came from unforced errors by the fifth-seeded Dementieva.

"I just was trying to go for the winner and couldn't make it," Dementieva said. "I couldn't close the point." Jankovic entered the match with an 0-4 career record in major semi-finals, including losses at this year's Australian

Open and French Open. But she kept tracking down balls, running along the baseline and stretching her racket, extending points until Dementieva missed.

Several times, Jankovic wound up doing the splits at the end of a point. Jankovic and Dementieva, the runner-up at the US Open and French Open in 2004, are probably the two best women's tennis players without a Grand Slam championship.

Both have a history of coming up jittery in the late stages of majors. Back and forth they went, swatting powerfully from the baseline, with the shot count often topping 20 on a single point.

That was partly due to good movement by both, but Jankovic in particular. She sometimes would bend over to catch her breath between points, or stop to chat with spectators.

When she got to set point in the first with Dementieva serving, Jankovic drew a time violation warning from chair umpire Lynn Welch for pausing to wipe away sweat with a towel.

The turning point might have come a little earlier, with Dementieva up 4-2 and love-30 on Jankovic's serve. Two more points, and Dementieva would have served for the opening set.

Instead, this is how things went: Dementieva missed three consecutive service returns, and Jankovic then won the game by ending a 21-stroke point with a backhand winner. Appearing rattled, Dementieva began the next game by double-faulting, and eventually was broken when a 67 mph serve put her on the defensive.

By now, Dementieva was looking up at her mom in the stands more frequently. While she broke Jankovic twice in the second set, Dementieva never was able to stay in front.