Serena Williams moved within one victory of a fifth Wimbledon singles title with a formidable straight sets win over Victoria Azarenka.
The American produced a Wimbledon record of 24 aces to overpower Azarenka 6-3 7-6 (8-6) and set up a meeting with Poland's Agnieszka Radwanska.
Third seed Radwanska convincingly beat Angelique Kerber of Germany 6-3 6-4 to reach her first Grand Slam final.
"She's unbelievable. She's playing great," said Williams of Radwanska.
The American served beautifully throughout on Centre Court to surpass her previous Wimbledon women's record of 23 aces, set in the third round last week, and in the process took her tally of aces at this year's Championships to 85.
Radwanska, the first Polish woman to reach a Grand Slam final for 75 years, performed with verve and poise during her win but has not won a set against Williams in their previous two meetings, including a quarter-final defeat at Wimbledon in 2008.
Williams, who hit 45 winners during her demolition of second seed Azarenka, expects her opponent to return well on Saturday.
"She's going to get every ball back," said the 30-year-old, who will equal sister Venus's tally of five Wimbledon singles titles should she win on Saturday.
"I've been working so hard, I really wanted it. I got a little tight in the second set. I was looking too far in the future. I was so close, but I can't do that."
Williams, bidding for a 14th Grand Slam title, was frighteningly good in the first set, producing eight aces and 20 winners during 33 minutes of almost faultless tennis.
Her serve seemed impregnable and when she broke Azarenka in the third game of the second set with a delightful forehand return, victory seemed a matter of routine. Williams celebrated going 3-1 ahead with a wild roar while the onlooking Venus proudly applauded.
But Australian Open champion Azarenka, who will return to the top of the women's rankings should Williams win on Saturday, temporarily halted the sixth seed's momentum by breaking in the sixth game to force a second-set tie-break.
The 22-year-old from Minsk saved one match point but netted a tame backhand to allow Williams to serve for the match, which she did with a stylish ace.
Earlier on Centre Court, Radwanska needed only one hour and nine minutes to secure victory.
It did not look promising for the world number three when she was broken early in the opening set but she hit back with breaks of her own in the sixth and eighth games on her way to winning five games in a row, with her relentless tennis forcing her German opponent into a number of errors.
The 23-year-old, who will go top the world rankings if she defeats Williams in the final, admitted nerves played a part in her poor start.
She said: "You really want to try your best but sometimes you want it too much and your hands are shaking. After that I concentrated on every point.
"I had a tough quarter-final and it was good to have a day off and rest because it's always tough against Angie.
"We are really good friends but on court we're opponents and you're trying everything to make the final."
Radwanska concluded the first set with an ace and decisively broke in the sixth game of the second set.
She secured victory when a disappointing Kerber - hoping to become Germany's first women's finalist since Steffi Graf 13 years ago - followed a wayward forehand with a backhand into the tramlines.