Great Britain will reach the last four if Germany beat Canada on Thursday.

Evans had beaten Isner in the singles but Cameron Norrie lost to Fritz.

That meant it all came down to the doubles, and when Evans and Murray went 4-2 down in the second set, it had looked as if they would not be able to repeat their heroics of the opening tie, when the pair grabbed a surprise victory over Germany.

But they broke back immediately and eventually took the second set to level, continuing their momentum in the match tie-break, in which they won the opening six points to take charge.

A tense finish ensued, however, as the Americans rallied to come within a point of levelling at 9-8 before the Britons sealed victory.

"We were just hustling. We just kept saying, 'Just try to get the ball back in play, start the point', and tried to use our skills after that," Murray said.

"We played an amazing point to break back at 4-2, got a bit of momentum and played a great [match] tie-break, which is ultimately what it comes down to so many times."

In a tight Group C, all four teams were going into their final matches with a chance of making the knockout round.

Evans had got GB off to a good start with a 6-4 7-6 (7-3) win over the big-serving Isner, with the British number two keeping up a perfect record of victories in the group stage.

But number one Norrie lost 7-6 (7-4) 3-6 6-1 to Fritz to send the tie into a doubles decider.

Victory means a nervous few hours as they wait to see how Germany - featuring world number three Alexander Zverev - fare against Canada, who have world number 11 Felix Auger-Aliassime and 14th-ranked Denis Shapovalov in their team.

Whoever goes through will face the Russian team in semi-finals after the defending champions advanced when Daniil Medvedev and Roman Safiullin beat Matteo Berrettini and Jannik Sinner 7-5 4-6 10-5 in the doubles to seal a 2-1 win over last year's runners-up Italy in Group B.

Spain and Poland booked their semi-final places at the season-opening men's team event on Wednesday.