Serena and older sister Venus won their semifinals Friday, setting up their third straight meeting in a Grand Slam final and fourth in the last five.
Serena, the 1999 Open winner, beat Lindsay Davenport 6-3, 7-5 after Venus, who won the tournament the last two years, beat Amelie Mauresmo 6-3, 5-7, 6-4.
On Saturday night, finally, one Williams will lose.
"Venus is playing well and I'm playing all right," Serena said with a wide smile before admitting the obvious. "I'm playing well, too."
Serena beat Venus in the championship matches at the French Open and Wimbledon this year after losing to her in last year's U.S. Open final.
"Venus is definitely right there if not a little bit ahead of me," Serena said. "That's what I keep telling myself so I can at least have a goal to work for."
On Friday, top-seeded Serena trailed 5-2 then won her last five games against Davenport and took nine of the last 10 points. Serena had 13 aces to just three for Davenport, the 1998 Open champion.
"I don't feel I'm out here to break up a Williams final," Davenport said. "I'm here to see if I can get to the finals"
The fourth-seeded Davenport, coming back from knee surgery in January, had three set points in the 10th game, but Serena held on to her serve.
Then Serena broke Davenport's serve at love and took a 40-0 lead in the deciding game. But she followed with just her second double fault.
Her final serve was a powerful one. Davenport did return it, but Serena smacked the ball back to the far corner of the court to Davenport's right.
Game, set, another all-Williams final.
On the court, Serena said she acts the same no matter who she's playing.
"My attitude is the same when I'm playing Venus because she's my opponent," Serena said. "And I'm sure her attitude is the same because I'm her opponent."
Venus doesn't understand why their monopoly is considered by some to be bad for tennis.
"When you win, there's a problem. When you lose, there's a problem," she said with a smile. "So what do you want me to do?"
Serena missed the Australian Open, the year's first Grand Slam, with an ankle injury.
"After I twisted my ankle in Australia, I just changed things," said Serena, whose reaction to her win was much more exuberant than Venus'. "I was more focused. I just decided I wanted to be the best at what I do."
Venus shook off a blister and spotty play to outlast Mauresmo.
The harder-serving Venus had only three aces, the same as Mauresmo. And she had 10 double faults to four for the 10th-seeded Frenchwoman.
Venus also had more unforced errors — 44-35 — and was outplayed at the net. Mauresmo complained in vain about several calls that went against her and replays showed she was right on some of them.
Venus remained calm when she struggled.
"I keep telling myself that it's just a game and go out there and have fun," she said. "It was hard to hold the racket at times, but you only get one chance at the final and you try to take it."
She had her right hand taped twice by WTA trainer Laura Eby.
The first time was before the 12th game of the second set. Venus had her service broken in that game, losing the set.
"In the middle of that second set, I really found my rhythm and really got into the match," Mauresmo said.
The second taping came before the fourth game of the third set. Again, Mauresmo broke service to tie the match at 2-2.
The turning point came in the next game when Mauresmo fell behind 0-40. She followed with two aces, then double-faulted to give the game to Venus.
Both players held serve for the next four games, leaving Venus ahead 5-4. Then Mauresmo, who lost to Serena in the Wimbledon semifinals, nearly evened the match.
She had three break points in the final game, but Venus saved them all with two serves of 116 mph and an ace at 114. That's when Venus really reared back and fired in a 122-mph serve to reach match point as Mauresmo barely got her racket on the ball.
Then Venus won the next point and her 20th straight U.S. Open match. She's also 35-3 in her career at the tournament.
Mauresmo held two fingers close together to indicate how tight the match was: "It's just this much and next time I'm sure it's going to go my way."
And she had plenty of support in the crowd. "Allez Amelie" ("Go Amelie"), one fan shouted.
"It felt great, actually, to play an American and feel the crowd behind you," Mauresmo said.