Venus Williams winced with each serve and doubled over to clutch her stomach after stretching for shots.
She was in so much pain, she barely could lift her racket bag after the match.
Refusing to succumb to a strained muscle or to Kim Clijsters' persistent strokes, Williams erased a big deficit and won 4-6, 6-3, 6-1 Thursday to set up a second straight Wimbledon final against her sister Serena, the defending champion.
In the first semifinal, Serena turned a rematch against French Open champion Justine Henin-Hardenne into a mismatch, winning 6-3, 6-2. Henin-Hardenne snapped Serena's 33-match Grand Slam winning streak a month ago in the semifinals at Paris.
Venus' fourth-round loss in the same tournament marked her earliest exit from a major in two years, and the abdominal strain that hampered her there flared up during the third game against Clijsters.
The 2000-01 Wimbledon champion took a medical timeout and was seen a second time by the trainer. And then came an hour rain delay after the first set.
"The rain saved me," Venus said. "I couldn't calm myself down. I was just so worried about the injury. Serena came in and talked to me. I went out and talked to my mom and my other sisters.
"My mom said: `sJust pray and calm yourself down. If you're going to play, play. If not, don't do it.' Finally, after about half an hour, I was able to come to terms with it."
She also got more help from the trainer, including a tight wrap on her midsection. Gasping for air between points and leaning on her racket like a cane, Venus twice fell behind by a break in the second set. But she broke back both times, kept whipping winners, and somehow reeled off 10 of the last 11 games to cap a dramatic victory.
"I'm really glad that the third set didn't go any further," fourth-seeded Venus said. "I was really blessed that I was able to get those games quickly."
When the Williams sisters play today, they will be facing each other in a major final for the sixth time. The family will gain its fourth Wimbledon trophy in a row.
Venus won the 2001 US Open final, the first between siblings at a major since 1884. But Serena won their next four Sister Slam finals, from last year's French Open through this year's Australian Open.
"I'm excited to be in the final again of a Grand Slam," said Serena, who will keep her No. 1 ranking. "I was able to realize at the French that you can't always make it to the final. So now that I'm back, it's definitely exciting. It's just another step, another day to keep fighting."
She was speaking before Venus took to Centre Court for what turned out to be the day's highest drama, with two top players trading sizzling strokes as the light faded.
In the third game, Venus aggravated an abdominal strain while serving and started bending over or rubbing her stomach after points. She cringed after hitting an overhead in a game she lost to fall behind 5-4. It was a recurrence of the injury that forced her to quit during the final of a tournament in Poland two months ago and limited her French Open preparations.
"As a rule, I never play with pain. I generally retire immediately. I've never been taught to play with pain," Venus said. "I just felt this time -- I just wanted to win, basically."
After the rain, the players traded four straight breaks to 3-3 in the second set. And then, suddenly, Venus began to make a dent, holding for 4-3 and breaking to 5-3 by running to the doubles alley for a great backhand retrieval that surprised Clijsters, who missed a forehand.