Having suffered defeat in both singles rubbers yesterday, the hosts knew nothing but a win would do and they halved the deficit to 2-1 with a battling 6-1, 3-6, 6-4, 6-4 triumph.

The main question before the contest got underway in the Scottish city was whether Olympic and Wimbledon champion Andy Murray and Juan Martin del Potro would take to the court after they were involved in a five-set epic yesterday, won by the Argentine, which lasted more than five hours.

Murray had admitted following the defeat that it would be "difficult" to play doubles but he opted to partner his brother, and it paid dividends for the British team, who will still need to claim victory in the concluding two singles matches tomorrow if they are to progress to the final.

"It's going to be tough," said 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."

Andy and Jamie Murray, who came into the tie having won the US Open men's doubles title with Brazilian partner Bruno Soares, started brightly and managed to keep their composure, despite dropping the second set on their way to sealing a vital win.

British captain Leon Smith is confident Murray, the current world number two, can pick himself up again when he faces Guido Pella in tomorrow's opening singles rubber.

"We're going to need the Glasgow roar tomorrow," he said.

"Everyone is tired - it's that stage of the season. 

"It's the same for their team, but if there's somebody you want going out to get the first rubber on the board, it's Andy Murray."

In the other semi-final taking place this weekend, Marin Cilic and Ivan Dodig moved Croatia to the brink of the final as they earned a superb victory over the French pairing of Nicolas Mahut and Pierre-Hugues Herbert, the world's top ranked doubles team, at the Kresimir Cosic Hall in Zadar.

The momentum in the closely-fought contest continued to change as both duos looked to seize the initiative but it was the Croatians who got the win in front of their home crowd, emerging on the right side of a 7-6, 5-7, 7-6, 6-3 scoreline.

Croatia have a 2-1 lead going into tomorrow's final day.