The prospect of turning the U.S. Open's prestigious center court into his own family playground has enticed Richard Williams for years, ever since he watched a women's tennis match on television in 1979.

When it was over, the winner was presented with a check for $48,000. Williams was making $52,000 a year. He did the math.

"I went and told my wife that we had to have two more girls and make them tennis players," said the enigmatic Williams, who already had three daughters. "I was 37 years old and knew nothing about tennis, but I thought we could teach them and they would win [the U.S. Open.] I thought it would happen a little bit earlier, but now is fine if it happens."

Twenty years later, prize money is a little better -- the winner of this year's U.S. Open women's championship gets $750,000 -- and Richard Williams has two chances to meet his goal. His youngest daughters, Venus and Serena, have grown up to be the high-energy, hard-serving, beaded-haired, body-conscious teenage sensations of women's tennis. In the last few years they have galvanized the sport as they have completely reshaped it, one pounding groundstroke at a time. Now they are one win away from playing each other in Saturday's women's championship. If they make it, they will be the only sisters to play each other in a Grand Slam final since Lillian and Maud Watson squared off in the first Wimbledon final in 1884.

On Friday, the sisters will play in the semifinals, with Venus, 19, facing top-seeded Martina Hingis, and Serena, 17, staring down defending champion Lindsay Davenport. The 19-year-old Hingis is the No. 1 player in the world and has five Grand Slam titles; the 23-year-old Davenport is ranked No. 2 after winning Wimbledon earlier this summer.

The Williams sisters' credentials are not quite so lofty; Venus is ranked No. 3 and Serena is No. 7, but neither has won a Grand Slam tournament. (The Australian Open, the French Open, Wimbledon and the U.S. Open comprise tennis's grand slam.) Still, they've earned more than $4.3 million in their brief pro careers and each has been building toward a breakthrough this summer.

"If you're playing Serena, honestly, even on a bad day I'm tough to beat," said Serena after dispatching nine-time Grand Slam winner Monica Seles in the quarterfinals on Wednesday. "I still have one more match to go, and if I can do well in this match, then I know playing Venus will be great."

At 5 feet 10, 145 pounds, Serena is shorter than the lanky 6-2, 170-pound Venus, but long workouts and a thicker body frame have enabled her to match her sister's imposing presence. They both play a power game that relies on getting to shots quicker than their opponents and hitting them back harder, and they both have a serve so strong it practically strips the yellow fuzz off the balls.

But it is their flair for the dramatic, their outspoken father and their unorthodox appearance that have built them as much celebrity as their tennis skills. Already unusual in a mostly white sport, the Williamses have made themselves stand out even more with the striking beads they wear in their hair and their flashy on-court clothes, many of which they design themselves.

They have attracted fans to tennis who have never watched it before, from young black girls to grizzled white men.

"We definitely have a large impact," Venus said. "Before, you never saw that many black people at a tennis match. But now people are watching what Serena and I do. I guess they want to be a part of it."

This is what Richard Williams, the son of a Louisiana sharecropper, had hoped for when he stuck rackets in each girls' hand at the age of four. The family was then living in the inner-city Los Angeles neighborhood of Compton, so Richard would take them to the public courts and coach them himself. He and his wife, Oracene, still coach the girls, although they now live on a 10-acre estate in Palm Beach, Fla. The family often travels together, with Richard sometimes feeding the frenzy of attention with his eccentric comments.

"My dad is friendly with everyone -- he'll talk for hours and hours if you have the time," Venus said. "He's a parent, and he's doing what he loves. He's making sure we're okay."

As the older of the sisters, Venus has borne the brunt of the pressure that comes with being a sensation, and she has matured under the bright glare of the spotlight. Since reaching the U.S. Open final in her first appearance here in 1997 -- her only Grand Slam final -- she has become more careful on the court and more circumspect off of it. Her sharply angled face often bears a fierce stare of concentration. Able to follow in her sister's wake, Serena is more giddy and outgoing, saying at a recent tournament that her house was going to have a "lot of mirrors" when she got older because "I love to get my daily dose of me." After defeating Seles, she let out a yelp of joy, raising both arms way above her head as if to invite the crowd to celebrate along with her.

From the corner of the stands, Venus was one of the people clapping loudest. As different as the sisters are, they are extremely close. They practice together, go shopping together and even play doubles together, giving them a support system that makes players like Seles envious.

"They have such an advantage to have each other just in terms of company, practice, pushing each other," Seles said. "I don't think it can get better than that."

Seles wouldn't be surprised if that dream Richard Williams had two decades ago eventually comes true, saying that "as a player, when you play somebody, you can kind of sense that, and definitely now Serena and Venus are up there." The sisters, who have played each other in one tournament final -- Venus won, 6-1, 4-6, 6-4, in Key Biscayne, Fla. -- wouldn't be surprised either.

"We always thought we would -- that's what we were practicing for," Venus said when asked if she used to dream about playing Serena for a Grand Slam title. "We had an aim and a goal. It was a given."