While most of the men found it tough going on day six of the season's final grand slam, Venus and Serena faced no such problems.

Venus overwhelmed Ukrainian Alona Bondarenko 6-2, 6-1, while younger sister Serena blew past Japan's Ai Sugiyama with an identical scoreline. "I'm definitely at my best now," seventh seeded Venus boasted after her 56-minute rout under sunny skies at the National Tennis Center.

Serena Williams of the United States hits a return shot to Ai Sugiyama of Japan during their match at the U.S. Open tennis tournament in Flushing Meadows in New York, August 30, 2008. [Xinhua/Reuters]

The 28-year-old, who will next face Polish ninth seed Agnieszka Radwanska, said she has added a little spice to her game since arriving at Flushing Meadows a decade ago.

"I understand the game more," Venus, who has dropped only 11 games in her three matches to date, said. "Trying different kinds of shots too, trying to add some variety."

Neither Venus nor fourth seeded Serena have lost a set during this year's tournament and are the only women left in the draw to have won the US Open previously.

Serena admitted she was "disappointed" at the chance to play Venus in the quarters.

"But I've had over a week to think about it. So right now I'm just hoping to win my next match," said Serena, whose next test will be against Severine Bremond of France.

Russian Dinara Safina, tipped by many as a potential champion here, almost became another big-name casualty before scrapping to a 3-6, 7-5, 6-2 win over Swiss teenager Timea Bacsinszky.

Former world No. 1 Amelie Mauresmo reached the fourth round of a grand slam for the first time in over a year when she won 6-4, 6-4 against Julie Coin, the 188th-ranked Frenchwoman who had earlier stunned top seed Ana Ivanovic.

Mauresmo's opponent in the fourth round will be Italian No. 16 Flavia Pennetta, who rallied to beat Russian No. 19 Nadia Petrova 4-6, 6-4, 6-3.

(Agencies via Shanghai Daily September 1, 2008)