Serena Williams beat Zheng Zie of China in straight sets to set up a third meeting with Venus, her sister, in the final of the women’s singles at Wimbledon - the seventh time the siblings will have faced each other in a head-to-head fight for a grand slam title.

Serena, the two-time champion, overcame two rain delays and served 14 aces to beat Zheng in an entertaining encounter 6-2, 7-6 on Centre Court.

Serena was rarely troubled in the opening set of her match with Zheng and was simply too powerful for the world no 133, who had made her mark by knocking out top seed Ana Ivanovic in the third round.

“She pushed me and really played a great match,” said Serena of an opponent she had comfortably defeated in the first round here four years ago.

The second set, however, was much more competitive and Zheng was left to regret a great opportunity to take the semi-final to a decider when she held set point in the 10th game only for Williams to call on her powerful smash to rescue herself.

“She played like she had nothing to lose. I was able to hit a smash on that set point. I didn’t really want to go into a third set,” added the American.

“I’m looking forward to playing Venus in the final. She’ll be the toughest opponent I have faced."

The sisters were seeded sixth (Serena) and seventh (Venus) for the championships on the basis of their world rankings, rankings felt to be artificially low due to their limited schedule, but as, one-by-one, the top seeds fell by the wayside, their meeting in the final took on an air of inevitability.

Earlier, Venus, the defending champion and four-times winner, beat Elena Dementieva 6-1, 7-6, though the result was somewhat overshadowed by her subsequently taking offence at comments made in English by her beaten opponent at the post-match press conference, the Russian suggesting that the outcome of Saturday’s final was “going to be a family decision”.

Clashes between the pair have rarely been classics, though suggestions from some quarters that neither give their all at the same time were bitterly denied by Venus.

“I find the question pretty offensive because I’m extremely professional in everything that I do on and off the court,” she said.

“I contribute my best in my sport, and I also have a ton of respect for myself and my family. So any mention of that is extremely disrespectful for who I am, what I stand for, and my family. That’s pretty much how I feel about the whole subject."

The sisters have met 15 times before. Serena currently leads the series 8-7 but has emerged the winner on five of the six occasions the pair have met in Grand Slam finals, including the 2002 and 2003 finals at Wimbledon.