WIMBLEDON, England -- The Williams sisters moved closer to another Wimbledon final Tuesday, using their power tennis to cruise into the semifinals in straight sets.

Defending champion and four-time winner Venus Williams beat Thailand's Tamarine Tanasugarn 6-4, 6-3, and two-time champ Serena swept 19-year-old Agnieszka Radwanska of Poland 6-4, 6-0.

The Williams sisters are in opposite halves of the draw and could meet in Saturday's final. The two have met twice before in the Wimbledon final, with Serena winning both in 2002 and '03

"That would be amazing if we both were in the final," seventh-seeded Venus said. "I have to take it one more step and keep playing power tennis."

Venus next will face No. 5 Elena Dementieva, who wasted a 5-1 lead and two match points in the second set before beating fellow Russian Nadia Petrova 6-1, 6-7 (6), 6-3 to reach her first Wimbledon semifinal.

Sixth-seeded Serena will play Zheng Jie, who became the first Chinese player to reach the semifinals of a Grand Slam by beating Nicole Vaidisova 6-2, 5-7, 6-1. The 133rd-ranked Zheng is also the first wild-card entrant to reach the women's semis at Wimbledon and second at any Grand Slam.

"I think many people [will] watch this match in China," Zheng said.

The Williams sisters will be heavy favorites to set up their sixth Grand Slam final showdown. Serena leads 5-1 in Slam finals and 8-7 in overall matches.

Serena watched some of her sister's match while waiting to go on court.

It's been five years since Serena won the Wimbledon trophy, and her last Grand Slam title was at the 2007 Australian Open.

Neither of the sisters has dropped a set so far in the tournament, and their big serves and punishing ground strokes have put them a class above the rest of the field.

"I think I have a lot of power, so it helps," Venus said.