In a protracted afternoon of tennis, made longer by two rain delays, first Venus and then Serena won their Wimbledon semi-final matches to reach Saturday's championship match.

Venus defeated No.5 seed Elena Dementieva 6-1, 7-6 while Serena then struggled past unseeded, 133-ranked Zheng Jie of China 6-2, 7-6- winning on a double fault.

Big credit to the 22-year old from Cheng Du, who's run was historic: In the third round she became the first Chinese player ever to beat a reigning world No.1 when she uspet Ana Ivanovic and she was also the equal-lowest-ranked player to achieve the feat (Kim Clijsters did the same). Zheng eventually became her country’s first Grand Slam semi-finalist.

In case you missed it,, it will be the 16th meeting of the Williamses, with Serena leading 8-7. But because of upsets or fitness problems they haven't been able to negotiate a Grand Slam draw together since Wimbledon in 2003.

Four weeks ago both were bundled out of the French Open in the third round, but neither has lost a set in the six matches it took to reach this final. However, Serena came perilously close against the virtually unknown Zheng, who compensates for an extremely weak second serve with one of the best backhands on the WTA tour.

Several times she zinged backhand winners past Williams' groping racket, including the one that started her rally back from 2-5 in the tiebreak. She got to 4-5 when Williams returned long and then knotted the tie-break when Serena’s easy forehand went long.

The audience on the Centre Court, which seemed to be heavily sympathetic with the underdog, urged her on, but after Williams pulled ahead 6-5 with a 123 mph service winner that survived a Hawkeye challenge, Zheng took the balls and, on second serve, slapped a weak, perhaps nervous shot into the net.

Serena went into a celebration on court, but things were much more reserved in the players’ box, where sister Venus simply stood up, not applauding, and accepted congratulations from friends in anticipation of their final.

The Williams-Zheng match had been twice interrupted by rain and the second delay came with the second set at 5-5 and Zheng serving at 40-30. When the two women resumed play, one hour and 21 minutes after they'd fled the rain, they punched and parried through six deuces before Zheng pushed Williams from one side of the court to the other before slamming away an overhead. Williams then held serve at ad and they went into the decisive tiebreak.

Earlier, Venus seemed to have an easy time with Dementieva, who also has a long history of serving problems. But after losing her serve for the fourth time, early in the second set, the Russian buckled down her game.

She broke back to 2-2, but could never get a lead and play from strength.

Both Williams girls continue to have health issues, but it hasn't kept them from playing singles and doubles, and they're still alive in the doubles draw.

Venus hinted a few days earlier that she is on medication for a continuing problem with anaemia. Serena, meanwhile, played this match with both ankles and her right wrist taped and a heating pad taped to her right hamstring.