Holders Czech Republic showed how tenaciously they will fight to retain the Davis Cup as Tomas Berdych and Lukas Rosol won a record-breaking doubles match against Swiss duo Marco Chiudinelli and Stanislas Wawrinka.
Their seven hour two minute victory, including a 24-22 final set, put the Czechs 2-1 ahead in the tie in Geneva and they need to win only one of the two singles rubbers.
The Czechs needed 13 match points before the Swiss finally cracked but for France and Serbia things were far more straightforward as they took unassailable 3-0 leads in their matches against Israel and Belgium respectively.
Argentina also clinched a quarter-final berth by taking a 3-0 lead against Germany.
Top seeds Spain will try to stay alive in Canada having lost both of Friday's singles.
Czech Rosol was formerly best known as the man who stunned Rafa Nadal at Wimbledon last year but now he has another claim to fame after Saturday's epic doubles win with Berdych.
Their 6-4 5-7 6-4 6-7 24-22 win was achieved despite fierce home support and was sealed by a double-fault.
Wawrinka, who lost a five-set epic against Novak Djokovic at the Australian Open, now needs to recover his energy to take on Berdych again in Sunday's first reverse singles.
French duo Julien Benneteau and Michael Llodra thrashed Israel's Dudi Sela and Jonathan Erlich 7-6 6-1 6-0 in Rouen to give France a 3-0 lead.
Jo-Wilfried Tsonga and Richard Gasquet both comfortably won their singles matches on Friday.
World number one Djokovic will be spared more exertion on Sunday after 2010 winners Serbia built a 3-0 lead against Belgium when Viktor Troicki and Nenad Zimonjic came through in four sets against Steve Darcis and Ruben Bemelmans.
Djokovic, playing his first match since winning the Australian Open for a third consecutive year, crushed Olivier Rochus on Friday on an indoor claycourt in Charleroi.
France, bidding for a 10th Davis Cup title, will face Argentina in the quarter-finals after the south Americans clinched victory with a day to spare against Germany.
David Nalbandian and Horacio Zeballos delighted the Buenos Aires crowd with a 6-1 6-4 5-7 6-2 victory against Christopher Kas and Tobias Kamke.
Kamke stood in for Philipp Kohlschreiber, who retired in the fifth set of Friday's opening singles with a pulled hamstring against Carlos Berlocq.
Germany's captain Carsten Arriens said the home crowd at Parque Roca had been fantastic in their support for Argentina, adding he would love to have a CD of their chants.
"Argentina will need that to play France," he said.
Serbia will face the United States if they complete victory over Brazil, having forged a 2-0 lead.
Elsewhere, Austria kept their tie against Kazakhstan alive as Julian Knowle and Alexander Peya won the doubles to leave the hosts leading 2-1 in Astana. Italy lead Croatia 2-1.