NEW YORK - Thanks to her latest easy victory, Serena Williams is one match from her fourth U.S. Open title and 15th Grand Slam trophy overall.

Williams wasted little time or energy while overwhelming 10th-seeded Sara Errani of Italy 6-1, 6-2 on Friday night to reach the final at Flushing Meadows.

Building a 38-6 edge in winners and smacking nine aces to raise her tournament-leading total to 50, Williams needed only 64 minutes to dismiss Errani, the runner-up at the French Open.

Not only has Williams won every set she's played over the last two weeks, she's dropped a total of only 19 games across six matches. It's part of a stretch of dominance that has carried her to a 25-1 record since a shocking first-round exit at the French Open in late May, the only time in 49 Grand Slam appearances that Williams lost her opening match.

Her recent surge includes titles at Wimbledon and the London Olympics.

"It's really awesome," Williams said in an on-court interview. "That is what I wanted, and what I dreamed of, all year."

It was 12 months ago that the American was stunned in straight sets the U.S. Open final by Sam Stosur. Williams' championships in New York came in 1999, 2002 and 2008.

In Saturday night's final, she will face top-ranked Victoria Azarenka of Belarus, who beat Maria Sharapova in three sets earlier Friday. Williams is 9-1 against Azarenka.

"Obviously, Victoria wants to win, too," Williams told the crowd in Arthur Ashe Stadium. "But I'm American, guys. Last one standing. Go USA!"

In many ways, her semifinal was a complete mismatch.

Errani had never been past the third round at the U.S. Open -- and never past the fourth round at any major tournament -- until this year. She reached the quarterfinals at the Australian Open in January, then made it all the way to the final at the French Open, losing there to Sharapova.

In her first 17 Grand Slam appearances, Errani was 15-17. She entered Friday 17-3 in 2012 at the sport's four most important tournaments.

Friday's match was only her second major semifinal, Williams' 22nd, and that disparity showed right from the outset.

Errani did not even come within a point of winning a game until she already trailed 5-0. When Williams netted a backhand, Errani got on the board at 5-1.

By then, the outcome was clear.

When Errani finally won a second game, getting to 2-1 in the second set with an inside-out forehand to hold serve, she let out a yelp and skipped toward the sideline.

Errani won the first point of the next game, too, with a well-angled groundstroke winner that made it love-15.

At that moment, it was as if Williams said to herself, "OK, enough is enough."

She won four points in a row to hold for a 3-1 lead like this: 102 mph service winner, 117 mph ace, 114 mph ace, 119 mph ace.

In the next game, Williams dumped a swinging backhand volley into the net and hopped in place, angry with herself, but then restored order to break yet again and make it 4-1.

Williams, who turns 31 on Sept. 26, is trying to become the first 30-year-old woman to win the U.S. Open since Martina Navratilova in 1987. She's also hoping to become the first woman with championships at Wimbledon and the U.S. Open since -- yes, you guessed it -- Williams did it in 2002.

Azarenka ousts Sharapova

Normally so good, so gritty, in the crucible of the third set, Maria Sharapova finally met her match against Victoria Azarenka.

Coming all the way back from a set and a break down, the top-seeded Azarenka prevailed in a stirring third, beating four-time Grand Slam champion Sharapova 3-6, 6-2, 6-4 on Friday to reach her first U.S. Open final.

"This one didn't go my way," Sharapova said. "Frustrating, but it's the game of tennis. A lot of swings in the match today. Certainly had the lead and the advantage."

Entering Friday, Sharapova was 12-0 in three-setters this year, and had won 78 consecutive matches in which she took the opening set, a streak dating to 2010. But Azarenka broke in the last game to push her own 2012 record to 12-0 in matches that went the distance.

"I didn't know that statistic," Azarenka said during an on-court interview. "It's pretty good."

Perfect, actually.

On Saturday, Australian Open champion Azarenka will play in her second major final of the season -- and career -- against 14-time Grand Slam champion Serena Williams. Seeking a fourth title at Flushing Meadows, the fourth-seeded Williams wasted little time or energy while overwhelming 10th-seeded Sara Errani of Italy 6-1, 6-2.

Williams, trying to become the first 30-year-old woman to win the U.S. Open since Martina Navratilova in 1987, compiled a 38-6 edge in winners in her 64-minute semifinal against Errani.

Since a surprising exit at the French Open in late May, her only first-round loss in 49 appearances at major tournaments, Williams is 25-1, including a title at Wimbledon and gold medal at the London Olympics.

Williams owns a 9-1 career record against Azarenka.

"I've got to do something different, to be honest," Azarenka said.

Asked whether she would watch video of their past matches, Azarenka joked: "Well, I don't want to be depressed."

Then again, the way Azarenka dealt with Sharapova, she's probably feeling pretty good about herself, too. She sure looked pleased while doing a little jig, then chucking some tennis balls into the stands, after the fading Sharapova's forehand sailed long on the final point of their 2-hour, 42-minute quarterfinal.

"I was just not trying to focus on the score," Azarenka said. "Trying to give whatever it takes."

Given a chance to rest for a bit after the second set by a 10-minute break requested by Sharapova under the extreme heat rule, both women came out swinging away in the third. Azarenka emerged from the locker room before Sharapova and took the opportunity to practice groundstrokes and serves with ballkids.

The third set was filled with high-quality play, made all the more impressive considering the sun, the swirling wind and what was at stake. They hit the ball hard. They chased down shots with terrific defence. Sharapova even shifted her racket from her right to her left hand during a couple of lengthy exchanges.

One particularly intense and riveting game came with Sharapova serving while trailing 2-1. Azarenka accumulated three break points, but Sharapova saved each, the last with a cross-court backhand winner. After a fifth deuce, Sharapova eventually held with a 109 mph ace, one of her eight in the match.

But the third-seeded Sharapova also double-faulted 10 times, a recurring theme ever since she returned from surgery on her right shoulder in 2008.

"I gave her too many free points," Sharapova said.

This has been a resurgent year for the Russian, who completed a career Grand Slam by winning the French Open in June, was the runner-up at the Australian Open and the Olympics, and briefly returned to No. 1 in the rankings -- a spot that now belongs to Azarenka.

"I'll take the results I had this year," Sharapova said.

She reached her first U.S. Open semifinal since winning the 2006 title thanks to overcoming deficits en route to three-set victories in the fourth round and quarterfinals.

But she didn't have one more late-match charge in her.

With a cloudless blue sky and the temperature approaching 90 degrees, Arthur Ashe Stadium was steamy when Sharapova and Azarenka got started, shrieking loudly with nearly every stroke.

Well, Sharapova was ready at the outset, anyway. Azarenka? Not so much.

Sharapova took 12 of the first 17 points, hitting deep, clean groundstrokes, while Azarenka needed 18 minutes to win a single game. When they met in the Australian Open final, Sharapova won a total of three games. She equaled that by the time she led 3-0 when Friday's semifinal was 11 minutes old.

Azarenka, who came in averaging 20 winners per match in the tournament, managed to produce merely one in the first set. She finished with 19, the same number as her unforced error count. It was Sharapova whose play determined the result on most points: She had 44 winners and 42 unforced errors.

When Sharapova broke Azarenka to go ahead 1-0 in the second set, she appeared to be in control. But that's when Azarenka really showed up, taking four consecutive games and six of the next seven.

"All heart," said Azarenka, a 23-year-old from Belarus.

"That's what I feel like we play for, we live for," Azarenka said, "to play on these big stages against such champions."

She'll get a chance to do that again Saturday against Williams.