Belarus sustained their giant-killing run in the Davis Cup on Saturday when Max Mirnyi and Vladimir Voltchkov grabbed a winning 3-0 lead against Argentina in the quarter-finals.
Brothers Mike and Bob Bryan combined to beat Jonas Bjorkman and Thomas Johansson 6-3, 6-4, 6-4 to give the United States a 2-1 lead over Sweden.
France gained the psychological edge in their tie in Lausanne after Nicolas Escude and Michael Llodra defeated Roger Federer and Yves Allegro 6-7, 6-3, 7-6, 6-3 to give the visitors a 2-1 advantage over Switzerland.
World Group newcomers Belarus, who had knocked out 2002 champions Russia in the first round, surged into the semi-finals of the men's team competition for the first time after Mirnyi and Voltchkov joined forces to overwhelm Agustin Calleri and Lucas Arnold 6-3, 6-4, 6-1.
Playing without the injured Guillermo Coria and David Nalbandian, the Argentines struggled to adjust to the fast carpet surface all weekend and failed to win even a set in the three rubbers.
Mirnyi lived up to his nickname of 'The Beast' as he helped hammer the Argentine duo with a combination of powerful serves and blistering groundstrokes from the baseline.
He was ably supported by Voltchkov, who delighted the capacity 4,800 crowd with his attacking netplay.
Belarus will be hoping to continue their astonishing run in this year's competition when they travel to either the United States or Sweden in September for the semi-finals.
Despite losing their service at the start of the first two sets, the Bryan brothers, the world's number one doubles team, were far too strong for Bjorkman and Johansson at Delray Beach, Florida.
World number three Andy Roddick can clinch the tie for the U.S. when he faces Bjorkman in the first of Sunday's reverse singles rubbers.
If Bjorkman prevails, Mardy Fish and Thomas Enqvist will contest the deciding fifth rubber.
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World number one Federer proved to be the weak link in the Swiss partnership as he was broken three times during the first three sets.
The Wimbledon and Australian Open champion failed to reproduce the form that had helped him to demolish Escude in Friday's singles.
Left-hander Llodra, winner of the Melbourne Park doubles title with Fabrice Santoro, was the architect of France's triumph, never dropping serve during the three-hour contest.
"I think the difference between the two pairs was that we were able to raise our level at the most important moments," said Llodra.
"The role of (France captain) Guy (Forget) was also very important, especially after we lost the first set. He got us into the right frame of mind for the second set."
Despite the setback in the doubles, Federer will go into his match against the 25th-ranked Arnaud Clement as a clear favourite. If Federer wins the match, the tie will go into to a live fifth rubber.
In Palma, Spanish pair Tommy Robredo and Rafael Nadal were leading Dutchmen John Van Lottum and Martin Verkerk by two sets to one when rain halted play in their tie.
The match will resume at 0830 GMT on Sunday before the reverse singles.
Spain went 2-0 up on Friday after Carlos Moya and Juan Carlos Ferrero had both claimed easy straight-set victories.