Serena Williams saw off a brave challenge from Elena Dementieva to reach her fifth Wimbledon final.

Williams saved a match point in the 10th game of the deciding set before prevailing 6-7 (4-7) 7-5 8-6 in two hours and 49 minutes on a sun-kissed Centre Court.

She will play sister Venus on Saturday in what will be a fourth all-Williams Wimbledon final after she destroyed Dinara Safina 6-1 6-0 in less than an hour.

Dementieva, the fourth seed, came out swinging and was rewarded with a break in the opening game but the Russian immediately surrendered her own serve as the first set settled into a pattern of powerful groundstrokes being traded from behind the baseline.

After the initial exchange of breaks, serve dominated with Williams looking particularly secure on her own delivery.

The American moved 0-40 ahead on her opponent's serve in the eighth game but was unable to convert any of her three break points as Dementieva reeled off five points in a row to hold.

Neither player had dropped a set on their way to the last four and it was no surprise when a tie-break was required.

And it was Williams who blinked first, her forehand deserting her as a series of errors gifted Dementieva the breaker by a 7-4 score.

The second seed re-asserted herself at the beginning of the second set, consolidating a break in the first game to open a 3-1 lead.

But Dementieva showed impressive resolve to recover the break in the sixth game and again to save a break point at 30-40 down to move 4-3 ahead.

However, Williams continued to force the pace and claimed a crucial break in the 11th game, confirmed via a challenge of an erroneous line call, to serve for the set at 6-5.

She was made to work hard, saving four break points - twice with an ace, but eventually closed out the second set with another booming ace to take the contest into a decider.

The third set was another closely-fought affair, Dementieva drawing first blood with a break in the fourth game before gifting it straight back.

At 5-4 down, Williams found herself under severe pressure and serving to stay in the match.

Dementieva's superb cross-court pass at 30-30 took her to match point but Williams saved it with a backhand volley and produced huge serves on the next two points to hold.

And Williams seized the moment again, breaking Dementeva for a 7-6 lead before serving out for an epic victory.

"It was really tough," Williams said. "She's been playing so well and has won a lot of matches against me in the past.

"I was not on my best game but my family were so positive. Elena played so well and we gave the crowd a wonderful match."