Venus handed defending champion Elena Dementieva her third defeat of the year, winning 6-3 6-3, and top seed Serena withstood a strong challenge from Serbian Ana Ivanovic to advance 6-4 6-4.

"Obviously she's been playing great this year and she has the game to control the match," Venus told reporters.

The sixth-seeded American took a 3-0 lead in the first set against Dementieva and went on to claim the final four games of the second.

"That's how she likes to play and that's how I like to play so I'm pleased that I was able to control the match," Venus added. "I would have liked to have broken serve a little more, but I was able to keep the pressure on."

World number one Serena had a little more difficulty in handling an aggressive and confident opponent, trailing 4-1 in the second set before sweeping the last five games.

"I thought she hit really, really hard and that was her whole game, to go for broke," the Australian Open champion said. "I like when people come to the net against me, I really do, and when I play her next I'll know more what to expect.

"I was feeling a little tired and the next thing I knew I was down 3-0 and I thought I'd just have to pull it together," Serena added.

The two sisters have a 9-9 record against each other. Venus beat her younger sister the last time they met, during the 2008 WTA Championships last November.

The other semi-final will be between unseeded Virginie Razzano of France and 16th seed Kaia Kanepi of Estonia.

Kanepi is expected to become the first Estonian to break into the world's top 20 after following up her victory against Jelena Jankovic with a 6-3 7-5 win over Russian qualifier Elena Vesnina. Razzano upset fifth-seeded Russian Vera Zvonareva 7-6 7-5.