The eighth-ranked Williams, looking for her second tournament victory in three weeks, used powerful groundstrokes to defeat the Frenchwoman in 68 minutes.

"The score looked easy but it was not. Every time I hit good shots she hit back," Williams said. "I tried not to make easy errors and make my shots."

Williams breezed through the first set in less than 30 minutes before being challenged by Pin in a long deuce in the fifth game. She hit a smash to go up a double break at 4-1 in the second set, then won the match after Pin's drop shot on match point went wide.

Williams will meet Flavia Pennetta of Italy on Saturday. Pennetta upset fourth-seeded Shahar Peer of Israel 3-6, 6-4, 6-2.

Williams and Pennetta met in a semifinal at the Korea Open in Seoul just two weeks ago — a match Williams won 6-2, 6-2.

"What can I say about her? She is a champion and she is going make the season ending championship for sure," Pennetta said. "It's going to be a tough match."

American Vania King, the defending champion, struggled to beat Dominika Cibulkova of Slovakia 6-7 (8) 7-6 (6) 7-6 (4) in a second-round match continued from Thursday. The Slovak had been leading 9-8 in the first set tie-break when rain interrupted play Thursday night.

King, however, bowed out of play with a back injury before she was to meet Zi Yan later Friday, giving her Chinese opponent a walkover to the semis.