STANFORD, California: Top seed Serena Williams surged into the quarter-finals of the 700,000-dollar WTA Bank of the West Classic on Thursday with a 6-3, 7-6 (9/7) triumph over Hungary's Melinda Czink.

Williams, an 11-time Grand Slam champion who owns this year's Australian Open and Wimbledon crowns, advanced to a meeting with Aussie Samantha Stosur.

Serena's elder sister Venus, whose seven Grand Slam titles include five Wimbledon crowns, had a later match against Russia's Alla Kudryavtseva to book her own quarter-final berth in the opposite half of the draw from Serena.

A victory would send Venus into a Friday quarter-final against Russian star Maria Sharapova, a three-time Grand Slam champion continuing her comeback from shoulder surgery.

Other matches later Thursday send Serbian fourth seed Jelena Jankovic against Germany's Sabine Lisicki and French eighth seed Marion Bartoli against American Melanie Oudin.