By Caroline Cheese
BBC Sport at Wimbledon
Serena thrilled to reach Wimbledon final
Serena Williams will face sister Venus for the third time in a Wimbledon final after bringing Zheng Jie's incredible run to an end with a 6-2 7-6 (7-5) win.
The sixth seed powered into a 5-2 lead in the first set before a shower forced the players off.
On their return, Williams took the set but the tenacious Zheng battled back and, after another rain delay, had a point to level the match.
However, the two-time champion edged a tight tie-break to seal victory.
Zheng pushed Williams all the way to the end, battling back from 5-2 down in the tie-break to 5-5.
But Williams' serve, impressive throughout, got her through, an ace setting up match point before Zheng's challenge ended disappointingly with a double fault.
"She definitely pushed me," Williams told BBC Sport.
"She played a great game and she played like she had nothing to lose and it's always fun to play an opponent like that.
"I didn't want to go three sets. I just wanted to close it out and hit some big serves."
Williams is through to her first Grand Slam final since the Australian Open last year and the first against her older sister since Wimbledon 2003.
"I'm happy to be back in a Grand Slam final but I want to do more than make the final," she said.
"Venus is a tough opponent, probably the toughest I've played."
Serena dismissed suggestions that the final might not see the two sisters at their best.
"I've had a classic final against her in the Australian Open - three very hard sets - and also the US Open was very high-quality tennis," she said.
"It's easy with sibling rivalry - I want everything Venus has, and plus we're good at this now - we just leave everything out on the court. Who doesn't want to win - this is Wimbledon."
Zheng beat top seed Ana Ivanovic and two other seeded players on her way to the semi-finals, the first Chinese player to do so in history.
However, it looked like her run might come to a juddering halt against Williams, who belted 14 winners in a one-sided first set.
But Zheng appeared to settle her nerves during a 37-minute rain delay and went toe to toe with the eight-time Grand Slam champion from the baseline.
The 24-year-old engineered a 4-2 lead, only to drop serve immediately, then - following the second rain delay - delivered a sizzling backhand return to set up a set point at 6-5.
But Zheng smashed a routine backhand into the net and though the crowd appreciated her battling fightback in the tie-break, it was Williams who prevailed.
Zheng said: "When I had set point in the second set I probably thought about it too much.
"Overall I'm quite happy with my performance today. On other surfaces I might have had a better chance, but on grass her serve was simply too big."