Tomas Berdych and Lukas Rosol won a Davis Cup doubles epic to give defending champions Czech Republic the edge over Switzerland as 2012 finalists Spain stayed alive in Canada.
Berdych and Rosol beat Switzerland's Stanislas Wawrinka and Marco Chiudinelli 6-4, 5-7, 6-4, 6-7 (3/7), 24-22 in the longest ever Davis Cup match on Saturday, an exhausting clash which took 7 hours and one minute.
The Geneva epic surpassed the previous record of 6 hours 22 minutes which John McEnroe needed to beat Mats Wilander 9-7, 6-2, 15-17, 3-6, 8-6 in a tie between the United States and Sweden in 1982.
Chiudinelli double-faulted on match point in a fifth set which lasted 3 hours 35 minutes, after he and his partner had saved 12 match points.
The win gave the Czechs a 2-1 lead in the World Group clash ahead of Sunday's reverse singles with the winners to play either Kazakhstan or Austria in the quarter-finals in April.
Wawrinka, the world 17, is due to face Berdych, the sixth-ranked player, in the first of Sunday's reverse singles.
"I have never experienced such a long tennis match. Victory tastes sweet but we still need a point," said Berdych. "It was extremely long, but we have quite a time to recover."
Wawrinka, who lost a five-hour epic to Novak Djokovic in the fourth round at the Australian Open last month, insisted he will be ready for Sunday's duel.
"I'm tired physically and mentally, but I'll be ready," said Wawrinka, his country's top player in the absence of Roger Federer.
In Vancouver, five-time champions Spain went into Saturday's doubles down 2-0 to Canada, who have never won a World Group clash.
Marcel Granollers and Marc Lopez kept the injury-depleted Spaniards' hopes alive as they battled to a 4-6, 6-4, 6-7 (4/7), 6-3, 6-2 victory over Daniel Nestor and Vasek Pospisil.
Missing top players Rafael Nadal, David Ferrer, Nicolas Almagro and Fernando Verdasco, Spain still faced an uphill task.
Granollers, the world number 34 who was beaten in straight sets by 166th-ranked Frank Dancevic on Friday, will have to dig deep to find the energy to take on Canada's world number 15 Milos Raonic, while Dancevic will take on Albert Ramos.
In stark contrast, Serbia and France cruised into the quarter-finals.
Serbia, the 2010 winners, reached the last eight for the fourth successive season when Viktor Troicki and Nenad Zimonjic, playing his 18th Davis Cup season, defeated Steve Darcis and Ruben Bemelmans 6-4, 6-4, 5-7, 6-4 to secure a 3-0 win over Belgium.
Serbia will face either the United States or Brazil for a semi-final place.
The US, a record 32-time champions, were 2-0 ahead of Brazil in Florida overnight but doubles specialists Bob and Mike Bryan suffered a stunning loss in the doubles.
Marcelo Melo and Bruno Soares claimed a famous 7-6 (8/6), 6-7 (7/9), 6-4, 3-6, 6-3 win to keep Brazil alive and condemn the American brothers to only the third defeat of their Davis Cup partnership.
In Rouen, Michael Llodra and Julien Benneteau teamed up to move France into the quarter-finals as they powered past Israeli pairing Dudi Sela and Jonathan Erlich.
The French duo won 7-6 (7/3), 6-1, 6-0 in the doubles to cement an insurmountable 3-0 lead in the tie and give new captain Arnaud Clement a debut victory.
France will now head to Argentina, who beat Germany 3-0, for their quarter-final.
David Nalbandian and Horacio Zeballos clinched Argentina's crucial point for an unbeatable 3-0 lead by beating Christopher Kas and Tobias Kamke 6-1, 6-4, 5-7, 6-2 in Buenos Aries.
Italy led Croatia 2-1 in Turin after Fabio Fognini and Simone Bolelli defeated Marin Cilic and Ivan Dodig 3-6, 6-1, 6-3, 7-6 (13/11) to edge closer to a last-eight tie against either Canada or Spain.