NEW YORK, Sept 3 (Reuters) - Two-times defending champion Serena Williams got off to a sluggish start before roaring past 11th seed Flavia Pennetta 6-3 6-2 to reach the semi-finals of the U.S. Open on Wednesday.
The top seed will meet Russian 17th seed Ekaterina Makarova, who reached her first grand slam semi-final with a 6-4 6-2 victory over 16thseed Victoria Azarenka, runner-up to Williams in the last two Opens.
The world number one, decked out in a black and white leopard print dress, lost her first two service games to Pennetta to fall behind 3-0 before snapping to attention and rattling off the next six games to claim the first set.
Determined to make up for a disappointing grand slam season in which she failed to reach the quarter-finals in any of the three previous majors, Williams broke her fellow 32-year-old in the fifth and seventh games to advance in 63 minutes.
"It feels so special to be back in the semi-finals for the first time this year," Williams, who has yet to lose more than three games in any set thus far in the championship, told the Arthur Ashe Stadium crowd.
"It's an unbelievable feeling. I'm so happy to have done it here."
Reporting by Larry Fine; Editing by Ian Ransom