Roger Federer and Andy Roddick were on course for the Wimbledon final when rain ended play early on a frustrating day in SW19.
Little action was seen on men's semi-finals day.
But in the 90 minutes or so that were possible, Federer and Roddick both moved ahead in the respective matches.
The players will now have to return on Saturday at 1200 BST to decide the final line-up.
Reigning champion Federer was just two games from victory against Sebastien Grosjean when the rain arrived for a second time at around 1915.
The Swiss top seed was leading by two sets to love and was 4-3 ahead with his
French opponent about to serve in the third when rain swept across the All
England Club.
Federer, who again looked highly impressive, had been leading 3-2 when the players were first driven off the court at 1330 for a four-and-a-half hour delay.
Due to that rain break, tournament organisers moved the other last-four clash between
second seed Andy Roddick and Tim Henman's conqueror, Mario Ancic, on to court one and it got under way just after 1800.
The American had claimed the first set 6-4 and was a break up at 4-3 in the
second - although unseeded Croatian Ancic had break point at 30-40 in the eighth
game when rain stopped play for the final time.
Both semis are due to resume at noon on Saturday, with the women's singles final between Serena Williams and Maria Sharapova still scheduled to begin at 1400 on Centre Court.
However, with the forecast for Saturday worryingly similar, it is possible that both
semi-finals may not be completed then.
Any serious disruption would even raise the possibility of the tournament
being extended into a third week, as happened in 2001 when the men's final between
Goran Ivanisevic and Pat Rafter was played on Monday.
In the mixed doubles, Martina Navratilova's hopes of retaining her title with Leander Paes were ended.
The pair were beaten 13-11 in the final set by the brother-sister duo of Wayne and Cara Black of Zimbabwe.
And in the boys' singles, British prospect Miles Kasiri took the first set against Scoville Jenkins on a tie-break before the match
was cut short by rain.
They will also return on Saturday - weather permitting.