By Larry Fine
NEW YORK, Sept 6 (Reuters) - Defending champion Serena Williams slugged her way to a U.S. Open title rematch against Victoria Azarenka as the top two seeds scored straight-set knockouts in their respective semi-finals on Friday.
World number one Williams beat fifth-seeded Li Na of China 6-0 6-3, overcoming some staunch resistance at the end, while Azarenka returned to the Flushing Meadows final with a 6-4 6-2 victory over unseeded Italian Flavia Pennetta.
After being overpowered in the opening set, Li battled valiantly in the second, saving six match points to hold serve in the eighth game before the top seed finally closed the deal on her seventh match point with and unreturned serve.
"It was a good match. It was tough at the end," Williams said. "I got a little nervous but I was able to close it out."
Williams, playing on the heels of a 6-0 6-0 quarter-final win against Spain's Carla Suarez Navarro, stretched her dominance to 24 consecutive games against Li and later said the Arthur Ashe Stadium crowd helped lift her.
"To hear constantly, 'Go Serena, go Serena,' it is really a pleasure. I hear young voices and older voices and it really makes me feel so special," said Williams.
The results set up the first back-to-back finals matchup since Serena and her sister Venus battled for the crown in 2002.
It could be a historic triumph for the 31-year-old Williams, who would register her fifth U.S. Open title and her 17th career grand slam singles crown with a victory in Sunday's final.
She would also become the oldest women's winner since tennis turned professional in 1968, supplanting Australian Margaret Court who was 31 years 55 days when she won in 1973.
Azarenka booked her return to the championship match by finally finding a way to hold serve in a match filled with 13 service breaks in the 18 games, eight coming against the Italian.
"I'm so excited. It's been a long road to the final. It's an amazing feeling, to fight for the trophy," said Azarenka, a former U.S Open junior champion and mixed doubles winner.
In the end, Azarenka's power was too much for the battling Pennetta, who returned from a serious wrist injury to reach her first grand slam semi-final.
There were five service breaks in a row before Australian Open winner Azarenka held to win the first set after an intense battle where the unseeded, 31-year-old Pennetta saved five set points before the Belarussian's final point service winner.
The second set followed a similar pattern, with three broken serves before Azarenka turned up the power, holding to go up 3-1 in the set and then breaking the 31-year-old Pennetta, ranked 83rd in the world, with a backhand winner.
Azarenka, 24, broke again for 4-1 and was on her way, ending the 94-minute match with a well-placed forehand that caused her to squeal with delight at reaching the final.
Earlier, Belarussian veteran Max Mirnyi captured his third U.S. Open mixed doubles title on Friday when he teamed up with Czech Andrea Hlavackova to beat American Abigail Spears and Mexican Santiago Gonzalez 7-6 (5) 6-3.
The 36-year-old Mirnyi's hat trick, each with different partners, was completed 15 years after his first Flushing Meadows triumph and was the 10th major doubles crown of his career.
He partnered with Williams to win the U.S. Open mixed doubles in 1998 and triumphed with Azarenka in 2007.
"Max was unbelievable, he covered 80 percent of the court and made it easy for me to make some great returns," said Hlavackova.
Hlavackova was due back on court later on Friday, along with Serena Williams, in the women's doubles semi-finals where Hlavackova and fellow Czech Lucie Hradecka were facing the Williams sisters. (Editing by Frank Pingue)