Serena remains on course in Miami

Serena Williams got some on-court help from her father, Richard

Serena Williams gave another ruthless display as she hammered Czech Nicole Vaidisova to reach the semi-finals of the Sony Ericsson Open in Miami.

The Australian Open champion, playing only her third tournament of the year, won 6-1 6-4 after facing triple break point at 4-4 in the second set.

"I play tough when I'm down, I can always count on my serve," she said.

Williams will next face Israel's Shahar Peer, who beat Italy's Tathiana Garbin 6-0 6-3.

Peer won the first nine games of the match on the way to her third semi-final of the year.

"I'm really happy," said Peer. "It's the first time getting to the semi-final in a big tournament and I was waiting for it long time."

The other semi-final sees Justine Henin face Russia's Anna Chakvetadze.