Serena Williams was a straight sets winner

"It was nice that I played well to get to the quarter-finals. I'm trying to keep my unforced errors down and play controlled tennis."

Serena Williams, the second seed, joined her sister in the last eight after a 6-3 6-3 win over Chanda Rubin.

Williams led 4-3 in the final set when rain disrupted proceedings but after the resumption she made short work of wrapping up the victory.

She broke Rubin, who won the Eastbourne tournament, in the sixth game of the match to clinch the first set.

Another break in the first game of the second set sealed her victory as she proved too strong for her compatriot.

The French Open champion will meet Daniela Hantuchova after the Slovakian beat former semi-finalist Jelena Dokic in straight sets.

Last year's beaten finalist Justine Henin needed two tie-breaks to beat 12th seed Elena Dementieva 7-6 7-6

The sixth seed had held the advantage in both sets before Dementieva broke back.

But the Russian's hopes of bringing the game to a third set disappeared when she served three double faults in the second set tie-break.

Fourth seed Monica Seles, of the United States, breezed through her fourth round match against Tamarine Tanasugarn.

She beat the 20th seed from Thailand 6-2 6-2.