Defending champion Serena Williams advanced to the US Open semifinals tonight, setting up a showdown against Kim Clijsters. The No. 2-seeded Williams beat No. 10 Flavia Pennetta of Italy, 6-4, 6-3 to improve her record to 23-1 in Grand Slam singles this season.
Williams has won three of the past four major championships. She is seeking her fourth US Open title and 12th Grand Slam overall. Clijsters, the 2005 US Open champion, beat No. 18 Li Na in straight sets earlier today.