Vaidisova's downed the unseeded Safarova 6-1, 6-4 after her compatriot was unable to reproduce the form that dumped defending champion Amelie Mauresmo out of the tournament earlier this week.

Vaidisova, 17, the youngest player left in the tournament, was an awestruck 11-year-old when she saw seven-time Grand Slam champion Williams, 25, practicing at Nick Bollettieri's tennis academy in Florida.

"I was definitely a big fan of hers, admired the way she played," she said.

But Vaidisova said she would not be intimidated facing the big American.

"I don't think I'll be going out there scared. But of course (I have) a lot of respect for what she's done."

Vaidisova, ranked number 12 in the world, said it was difficult to play against her friend Safarova in the quarterfinal.

"I've had some tough matches, a compatriot in the quarter-finals is always tough but I'm so happy I'm through, it feels great," she said.

"It's great for Czech tennis to have two quarter-finalists, one in the semis. Of course you don't want to play your friend but I'm just happy I got through it."