The United States stayed alive in their Davis Cup semi-final against champions Spain Saturday while four-time runners-up Argentina lost their doubles clash as well as Juan Martin Del Potro against the Czech Republic.
Bob and Mike Bryan beat Marcel Granollers and Marc Lopez 6-3, 3-6, 7-5, 7-5 on the clay courts of Gijon as the US cut the deficit to 2-1 against Spain.
The Olympic and US Open champions secured the crucial point which will mean the tie will be decided on Sunday with a place in November's final at stake.
Saturday's win took the Bryans' Davis Cup record to 20-2.
"They're pretty good in the clutch and they get us to Sunday when we're in this position all the time. We've got a chance," said US captain Jim Courier.
Five-time champions Spain are defending a run of 23 consecutive home victories in the tournament, a streak stretching back to 1999.
They had edged closer to a sixth final in 10 years on Friday when world number five David Ferrer beat Sam Querrey 4-6, 6-2, 6-2, 6-4 before Nicolas Almagro won a four-hour slog against John Isner, 6-4, 4-6, 6-4, 3-6, 7-5.
On Sunday, Ferrer will face Isner in the first reverse singles with Almagro scheduled to meet Querrey.
"Ferrer is such a warrior and John's going to have to play better than he did yesterday to stand a chance. He's a little bit more physically taxed than David is for sure," added Courier.
Argentina's hopes of making the final suffered a double blow when they slipped 2-1 down to the Czechs and then lost Del Potro through injury.
Tomas Berdych and Radek Stepanek eased past Carlos Berlocq and Eduardo Schwank 6-3, 6-4, 6-3 at a shell-shocked Parque Roca to take their Davis Cup record to 11-1.
World number eight Del Potro withdrew from Sunday's reverse singles with a wrist injury.
He will be replaced by world number 45 Berlocq in the clash against US Open semi-finalist Berdych, the sixth-ranked player, before Juan Monaco is scheduled to tackle Stepanek.
"Del Potro won't play so now we have to prepare with Berlocq. This is not what we expected, but we have two matches left. Del Potro is a significant loss but we will fight," said Argentina captain Martin Jaite.
Del Potro had defeated Stepanek 6-4, 6-4, 6-2 in the first singles rubber on Friday before Berdych levelled the semi-final, beating Monaco 6-1, 4-6, 1-6, 6-4, 6-4.
In the play-offs, where victory assures a place in the World Group for 2013, the Netherlands stayed in contention against Switzerland in Amsterdam when Robin Haase and Jean-Julien Rojer stunned Roger Federer and Stanislas Wawrinka 6-4, 6-2, 5-7, 6-3.
Federer and Wawrinka, who were doubles gold medallists at the 2008 Olympic Games, had both won their singles on Friday to give the Swiss a 2-0 lead.
The tie will be decided on Sunday when world number one Federer tackles Haase, the world 41, in the opening reverse singles, before Wawrinka takes on Thiemo de Bakker.
"It won't be an easy job but I will give it everything against Roger," said Haase.
"It's cold, the clay is heavy. I know he won't like that."
Belgium were promoted to the World Group after Olivier Rochus and Ruben Bemelmans beat Sweden's Michael Ryderstedt and Johan Brunstrom 6-4, 4-6, 6-3, 6-2 for an unassailable 3-0 lead in Brussels.
The result means Sweden will not feature in the World Group for the first time since 2000.
In Hamburg, Lleyton Hewitt and Chris Guccione enjoyed a 6-3, 6-2, 2-6, 7-6 (7/4) victory over Benjamin Becker and Philipp Petzschner to give Australia a 2-1 lead over Germany.
Jonathan Erlich and Andy Ram claimed a 5-7, 6-3, 6-3, 6-1 win over Tatsuma Ito and Yuichi Sugita to give Israel a 2-1 lead over Japan in Tokyo.
Elsewhere, Italy lead Chile 2-1 in Naples and Kazakhstan are 2-1 up on Uzbekistan in Almaty.
Canada lead South Africa 2-1 in Montreal while Brazil wrapped up a 3-0 win over two-time champions Russia in Sao Jose do Rio Preto.