Venus Williams ensured the Wimbledon final would be another family affair with a devastating performance against Russia's Dinara Safina.

Venus was a picture of power and precision as she defeated the world number one 6-1 6-0 in just 51 minutes, after sister Serena earlier had won an epic three-sets semi-final against Elena Dementieva.

There was no way Venus, the five-times champion, was being sucked into such a dogfight as she set up the fourth all-Williams final at Wimbledon.

Her semi-final was a much more subdued affair as she outclassed the world number one from the moment she settled into her big-hitting groove, winning the first nine points of the match and breaking the Safina service in the process.

Safina simply could not cope with the Williams serve, with one ace in the third game clocking in at 124mph, the fastest in the women's tournament.

Safina managed to get her side of the scoreboard ticking in the sixth game but it was no consolation as Venus, if anything, stepped up the power on her groundstrokes.

It was becoming a lesson in intimidation and when Venus promptly broke the Safina service at the start of the second set the match essentially was over.

Safina's mind appeared scrambled with the humiliation which was befalling her and Williams raced into a 4-0 lead, her opponent winning just four points in the process.

Unforced errors sprayed from Safina's racket as she began to panic, rushing her forehands, and a double fault in the fifth game handed Williams another break of serve.

The end eventually came when Safina dumped another forehand into the net to allow Venus to take the match, after which she expressed her delight at another all-Williams, all-American final on July 4.

Venus said: "This is my eighth final and it is a dream come true to have another opportunity to hold the plate up.

"I was able to stay focused and I have so much experience on this court. But the hardest part has to come, to play Serena in the final."

Earlier Serena had to save 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 against Dementieva.

The plucky fourth-seeded Russian came out swinging and was rewarded with a break in the opening game but she 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."