Andy and Jamie Murray kept Britain alive in its Davis Cup semifinal against Argentina, winning the doubles match in four sets to reduce the title holder's deficit to 2-1 on Saturday.
The Murray brothers beat Juan Martin del Potro and leonardo Mayer 6-1, 3-6, 6-4, 6-4 in front of a rowdy crowd in Glasgow.
The semifinal moves to the reverse singles on Sunday, when Andy Murray is set to play Guido Pella and Del Potro is down to play Kyle Edmund.
"Two-one down is a tough position to be in," Andy Murray said, "but we are closer than we were at the start of the day and I still believe we can come back."
Earlier on Friday, Del Potro ended Andy Murray's 14-match winning streak in the Davis Cup, coming through 6-4, 5-7, 6-7 (5), 6-3, 6-4 in 5 hours, 7 minutes to gain a measure of revenge after losing the Olympic final to Murray last month. It was the longest match of both players' careers.
Pella beat Kyle Edmund 6-7 (5), 6-4, 6-3, 6-2 in ther match.
The Murrays have a 6-0 record in Davis Cup doubles.
The winner will play either Croatia or France in the final.
Australia, Japan win
Doubles pair Sam Groth and John Peers beat Slovakia's Andrej Martin and Igor Zelenay 6-4, 6-2, 6-7 (3), 7-6 (2) on Saturday to clinch Australia's Davis Cup World Group playoff 3-0.
Slovakia saved a match point in the 12th game of the third set before winning the tiebreaker. But Australia dominated the fourth-set tiebreaker, winning the first five points.
The win with new captain lleyton Hewitt in charge ensured Australia, a first-round loser to the United States in February, will remain in the elite group of 16 countries for 2017.
Kei Nishikori and Yuichi Sugita beat Artem Smirnov and Sergiy Stakhovsky 6-3, 6-0, 6-3 as Japan won its Davis Cup World Group playoff 3-0 against Ukraine on Saturday.
The Japanese duo was in control from the outset and converted nine of 15 break point opportunities.
With the win, Japan secured its place in the World Group in 2017.
Croatia lead France 2-1
Marin Cilic and Ivan Dodig put Croatia 2-1 ahead in the Davis Cup semifinal against France by upsetting top-ranked doubles pair Nicolas Mahut and Pierre-Hugues Herbert 7-6 (6), 5-7, 7-6 (6), 6-3 on Saturday.
Cilic, who won his singles on Friday, replaced Marin Draganja and it proved to be an inspired choice.
Herbert, the more inexperienced of France's doubles pairing, sent his volley into the net to hand Croatia an unexpected victory at the Kresimir Cosic Hall in Zadar.