Updated

For the second time in two years the women's final at the U.S. Open will pit world No. 1 Serena Williams against former top-ranked star Victoria Azarenka.

Williams overcame Azarenka in three sets in last year's high-quality finale in New York City.

In Friday's semifinal nightcap, the top-seeded Williams whipped fifth-seeded Chinese star and fellow 31-year-old Li Na 6-0, 6-3, while the first semi on Day 12 saw the second-seeded Azarenka defeat unseeded Italian Flavia Pennetta 6-4, 6-2 at Ashe Stadium.

Williams took the first set at love in a mere 29 minutes against an overwhelmed Li on Day 12.

The Chinese star improved in the second set, as she broke Williams for a short-lived 2-1 lead. But Williams righted the ship by breaking right back on her way to a commanding 5-2 lead.

Williams and Li battled in a brilliant eighth game in the second, as the Chinese veteran saved a whopping six match points on her serve.

But the match came to an end in the next game, as Williams served her way into the final, converting on a seventh match point when Li netted one final forehand return.

"It was tough at the end," Williams said. "I got a little bit nervous, but I was able to close it out finally."

Williams needed 1 hour, 27 minutes to move on, as she broke Li five times while coughing up her serve only once.

The high-flying Williams improved to 9-1 lifetime against Li, including a perfect 4-0 mark in Grand Slam action.

The former French Open titlist Li was this year's Australian Open runner-up to the two-time reigning Melbourne champion Azarenka. She's now 3-2 in her career Grand Slam semis, with Friday marking her one at the U.S. Open.

The amazing Williams will now play in her 21st career Grand Slam final, seeking a 17th major title. She owns 54 career titles overall on the WTA circuit, including eight already in 2013. She was the French Open champion in June and currently holds half the major titles.

Williams is 4-2 in her U.S. Open finals, but has never titled back-to-back in Flushing. She's now 71-9 overall at the Open.

The powerful American is a sizzling 66-4 overall this year.

Meanwhile, the Belarusian stalwart Azarenka needed six set points and 52 minutes to win the first set against the 83rd-ranked Pennetta. The second set, however, was another story, as Azarenka cruised through that one in 42 minutes.

Serving for the match, Azarenka converted on her third match point with a solid forehand winner. The shrieking Belarusian broke her Italian counterpart eight times, while Pennetta tallied five breaks in a losing effort.

The slightly off Azarenka prevailed despite committing 25 unforced errors while striking only 15 winners and improving to a tour-best 31-1 on hardcourts this year.

"It was a little bit tricky," Azarenka said. "I couldn't find my rhythm at the beginning. I felt I was rushing too much. I couldn't really put the ball in play. It's good I stayed tough, played well in the return game at important moments."

The 31-year-old Pennetta is a former top-10 star who was playing in her first- ever Grand Slam semi. She's reached at least the quarterfinals in four of her last five trips to New York. The Italian missed last year's Open due to a wrist injury.

Azarenka is now 2-1 lifetime against Pennetta, who was the first-ever Italian woman to crack the WTA's top 10 back in 2009.

The 24-year-old Minsk native Azarenka will appear in her fourth career Grand Slam final, seeking her third title and first outside of Melbourne. She's 17-13 in her career finals overall, including 3-2 this season.

Azarenka has now reached four of the last eight women's Grand Slam finals.

Williams is 12-3 lifetime against Azarenka, but the Belarusian has won two of their three meetings this year -- all in finals. The American great, however, is a dominant 7-0 in their career Grand Slam matchups.

The 2013 women's U.S. Open champ will earn $2.6 million. Williams would claim an additional $1 million as a result of capturing the U.S. Open Series.