Britain kept their hopes of retaining the Davis Cup alive thanks to a terrific backs-to-the-wall effort from brothers Andy and Jamie Murray yesterday.

The Scottish siblings had to win their doubles rubber to stay in the tie against Argentina and battled hard to reduce the overall deficit to 2-1 with a four-set triumph over Juan Martin Del Potro and Leonardo Mayer to line up a compelling final day.

Andy, so often the British Davis Cup hero, was again the toast of the team, returning to the fray 19 hours after losing the longest match of his career to help secure a 6-1 3-6 6-4 6-4 win with his elder brother.

The victory enabled him to earn a measure of revenge over Del Potro who had beaten Andy in an epic five-setter on Friday that had lasted five hours seven minutes.

It sets up a fascinating third day with Andy having to fight off exhaustion when he seeks to send the tie to a deciding rubber by beating Guido Pella in the first of  reverse singles.

If he prevails it will then be Del Potro’s turn to battle against weariness when he could face Kyle Edmund, who lost his opening rubber against Pella, in a decider.

Britain captain Leon Smith, though, could plump instead for Dan Evans who came so close to toppling eventual winner Stan Wawrinka in this month’s US Open.

“It’s going to be tough,” said Andy Murray. “I’m obviously tired just now.

“I know how their players will be feeling too. I’ll try and get through the first match and see what happens.”

Other semi-final: Croatia vs France 2-1.