NEW YORK -- Serena Williams' U.S. Open title defense ended in bizarre, ugly fashion Saturday night, when she was penalized a point on match point after yelling and shaking her racket in the direction of an official who called a foot fault.
Williams lost to unseeded, unranked Kim Clijsters 6-4, 7-5 in a taut semifinal that featured plenty of powerful groundstrokes by both women. No one will remember a single shot that was struck, though, because of the unusual, dramatic way it finished.
With Williams serving at 5-6, 15-30 in the second set, she faulted on her first serve. On the second serve, a line judge called a foot fault, making it a double-fault -- a call rarely, if ever, seen at that stage of any match, let alone the semifinals of a Grand Slam tournament.
That made the score 15-40, putting Clijsters one point from victory.
Instead of stepping to the baseline to serve again, Williams went over and shouted and cursed at the line judge, pointing at her and shaking a ball at her.
Dropping the f-word liberally, Williams said, "I swear to God I'm [expletive] going to take this [expletive] ball and shove it down your [expletive] throat, you hear that? I swear to God."
The line judge was called over to the chair umpire, and tournament referee Brian Earley joined in the conversation. With the crowd booing -- making part of the dialogue inaudible -- Williams then went over and said to the line judge: "Sorry, but there are a lot of people who've said way worse." Then the line judge said something to the chair umpire, and Williams responded, "I didn't say I would kill you. Are you serious? I didn't say that." The line judge replied by shaking her head and saying, "Yes."
Williams already had been given a code violation warning when she broke her racket after losing the first set. So the chair umpire now awarded a penalty point to Clijsters, ending the match.
"She was called for a foot fault, and a point later, she said something to a line umpire, and it was reported to the chair, and that resulted in a point penalty," Earley explained. "And it just happened that point penalty was match point. It was a code violation for unsportsmanlike conduct."
When the ruling was announced, Williams walked around the net to the other end of the court to shake hands with a stunned Clijsters, who did not appear to understand what had happened.
"I used to have a real temper, and I've gotten a lot better," Williams said in her postmatch news conference. "So I know you don't believe me, but I used to be worse. Yes, yes, indeed."
Williams denied threatening the line judge but would not reveal what she said.
"I didn't threaten [her]. I don't remember anymore [what I said], to be honest. I was in the moment. And, you know, everyone's fighting for every point. It was a really crucial point," Williams said.
Asked if the line judge deserved an apology, Williams added: "An apology? From me? Well, how many people yell at linespeople? Players, athletes get frustrated. I don't know how many times I've seen that happen.
"All year I've never been foot faulted, and then suddenly in this tournament they keep calling foot faults. I said something that I guess they gave me a point penalty for. Unfortunately it was on match point."
Lost in the theatrics was Clijsters' significant accomplishment: In only her third tournament back after 2 1/2 years in retirement, the 26-year-old Belgian became the first mother to reach a Grand Slam final since Evonne Goolagong Cawley won Wimbledon 1980.
"The normal feelings of winning a match weren't quite there," Clijsters said. "But I think afterwards, when everything kind of sunk in a little bit and got explained to me about what happened, yeah, you kind of have to put it all in place, and then it becomes a little bit easier to understand and to kind of not celebrate, but at least have a little bit of joy after a match like that."
Clijsters hadn't competed at the U.S. Open since winning the 2005 championship. Now she will play for her second career major title Sunday against No. 9 Caroline Wozniacki, who beat Yanina Wickmayer of Belgium 6-3, 6-3 in the other rain-delayed women's semifinal.
Williams came into the day having won three of the past four Grand Slam titles, and 30 of her previous 31 matches at major tournaments.
Wozniacki, who converted six of 11 breakpoint chances, advanced to her first Grand Slam final, using her speed and steady play to overcome an early break in the final set.
"It's a dream come true to play the finals of a Grand Slam, and now I'm here," a beaming Wozniacki said. "So I mean, I have absolutely nothing to lose."
Wozniacki, a native of Odense, Denmark, covered her mouth after Wickmayer's forehand landed wide on the final point, and nearly broke down as she approached the net. She won the final four games of the match as Wickmayer struggled with her groundstrokes.
"She made not any mistakes," said Wickmayer, who committed 40 unforced errors to 14 for Wozniacki. "She just kept bringing the ball back and back. ... She was really fast."
The long weather delay and marquee matchup on the U.S. Open's main court set up a surreal scene at Armstrong Stadium, with a sparse crowd of about 500 in the stands at the start of the semifinal. After the prematch music stopped and before Wozniacki and Wickmayer walked through the tunnel, a concerned fan shouted "Quick, before it rains again."
Oops, too late.
Wozniacki walked to the net after the first point to complain to the chair umpire about the slick surface, and play was stopped for about 10 minutes while a light drizzle fell.
Wozniacki jumped all over Wickmayer when play resumed, breaking her four times and closing out the set when the Belgian dumped a volley into the net.
Wickmayer went ahead 3-2 with a break early in the second set but couldn't keep it up as Wozniacki turned up the pressure, setting up the match with Clijsters.
"We're both fighters," Wozniacki said. "We want to win. We want to, you know, win this Grand Slam, and it's going to be a tough match."
ESPN.com senior writer Greg Garber, the Associated Press and Reuters contributed to this story.