Neither will be playing in Saturday's final.
Elena Dementieva came close, though, getting within a point of beating one half of the Williams sisters, Serena , before losing 6-7 (4), 7-5, 8-6 on Centre Court.
"The only regret I have: Maybe I should take a little bit more risk on match point, should go down the line," said Dementieva, who led 5-4 in the third set but watched Serena return her passing attempt with a backhand volley winner. "I'm disappointed with the shot because I'm very surprised I didn't go down the line."
In the other semifinal, Venus Williams routed top-ranked Dinara Safina 6-1, 6-0, setting up a fourth Wimbledon final between the American sisters. Serena beat her older sibling to win the title at the All England Club in 2002 and '03, but Venus defeated her sister in last year's final to win her fifth Venus Rosewater Dish.
Serena nearly missed out on Saturday's Fourth of July party at the All England Club, but her serve came through even when her forehand wasn't working at its best.
"You know, I wasn't sure if it's Serena or Andy Roddick on the other side," Dementieva said of Serena's serve, which produced 20 aces in the match. "Even with that I was able to break her a couple of times and I was in the lead in the third set. Like I said, she's a fighter."
The match, pitting 10-time Grand Slam champion Serena against two-time major finalist Dementieva, produced some of the most exciting tennis of this year's tournament.
PATRIOTISM: Now that the Williamses have earned their places in the Wimbledon final, they're rooting for another American to make the men's championship.
Roddick plays Andy Murray, of Britain, today for a spot in Sunday's final.
"Nothing against Andy Murray, but I'm just rooting for the American," Serena said. "I really, really want him to do well."
Roddick, who lost in the 2004 and 2005 finals, is trying to become the first American man to win at the All England Club since Pete Sampras in 2000.
TWO AND OUT: James Blake and Mardy Fish let a two-set lead squirm out of their grasp, missing out on their first Grand Slam final.
The unseeded American duo lost to defending doubles champions Daniel Nestor, of Canada, and Nenad Zimonjic, of Serbia, 5-7, 3-6, 6-2, 7-6 (3), 10-8 in the semifinals.
The second-seeded Nestor and Zimonjic will play top-seeded Bob and Mike Bryan in Saturday's final.
The American twins beat Wesley Moodie, of South Africa, and Dick Norman, of Belgium, 7-6 (4), 7-6 (3), 6-4.