Elena Dementieva, the Olympic champion, left Switzerland's Patty Schnyder a breathless wreck as she reached the semi-finals with a brisk 6-2, 6-3 victory.

Just moments after being on the receiving end of the 76-minute battering, Schnyder tipped her hat to the Russian fifth seed. "It's the best she's played against me. I lost to a great champion today," Schnyder said, after she fell 10-7 behind in their head-to-head meetings.

"I played some really good games, but didn't end up winning all of them - there was not much I could have done differently. She didn't give me too many chances to step in or even breathe a bit during the rallies. She was just on top of me."

Dementieva, who extended her winning run to 11 matches said: "I really expected a tough match against her and I feel very pleased the way I was playing. It's important to win in two sets, especially coming from Beijing. Extra time for recovery, it's always good."

The 26-year-old Russian wasted little time in making her intentions clear as she broke the Swiss in the third game of the opening set.

Dementieva kept on cranking up the power and enjoyed an 80% success rate on her first serve, and with her groundstrokes also hitting the target, Schnyder was soon left deflated and Dementieva won cruised to victory.

"Today she had an unbelievably high percentage of first serve, it was pretty fast as well," said Schnyder, who at 29 was the oldest woman left in the draw. "Before I used to have more time against her, she would struggle a bit with her backhands. So she's really improved and is playing with so much confidence and playing really well."

Schnyder said this could be the year the Olympic champion finally lands her maiden grand slam crown, but world No.6 Dementieva, who will topple Ana Ivanovic as world No.1 if she wins this title, claimed: "I'm very excited to be in the semis, but I'm sure I need to improve my game if I want to go to the final. I'm not playing at my best ... I'm so far away from being perfect."

Meanwhile, Venus and Serena Williams will meet in the quarter-finals today after cruising through their respective fourth-round matches. Venus, the No.7 seed, beat Agnieszka Radwanska, of Poland, 6-1 6-3, while her younger sister defeated wild card Severine Bremond, of France, 6-2, 6-2 to set up their fourth meeting at the US Open.

Russian sixth seed Dinara Safina reached the quarter-finals for the second time in three years with a 7-5, 6-0 victory over Germany's Anna-Lena Groenefeld.