Croatia kept their Davis Cup hopes alive when Marin Cilic and Ivan Dodig won a doubles match in four sets against the US in Oregon.
Cilic was not expected to play doubles, but was drafted in at the last minute after Croatia lost both singles rubbers on Friday to slip to the brink of elimination in the quarter-finals.
And the 2014 US Open singles champion teamed up superbly with Dodig against American doubles specialists the Bryan brothers, Bob and Mike, winning 6-2 2-6 6-2 6-4 in Portland on Saturday (Sunday AEST).
"I played probably the best match in my life in doubles, especially at this kind of occasion," Cilic told the Tennis Channel.
The US lead 2-1 heading into Sunday's (Monday AEST) reverse singles, while Davis Cup holders Britain also enjoy a 2-1 lead in Serbia after Jamie Murray and Dominic Inglot won Saturday's doubles.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Rain meant only one of Friday's two scheduled singles were completed but Serbia quickly squared up the quarter-final on day two as Dusan Lajovic thrashed James Ward 6-1 6-3 6-2.
However, Murray and Inglot were too strong for veteran Nenad Zimonjic and Filip Krajinovic, winning 6-1 6-7(2) 6-3 6-4 to put Britain one rubber away from the semi-finals.
Serbia are without world No.1 Novak Djokovic while Wimbledon champion Andy Murray travelled with his British teammates but will not feature in the tie.
In other action Argentina lead Italy 2-1 in Pesaro while Wimbledon doubles champions Nicolas Mahut and Pierre-Hugues Herbert won Saturday's doubles to give France a 2-1 lead over the Czech Republic.
