Titleholder Britain won the doubles to lead Serbia 2-1 in their Davis Cup quarterfinal on Saturday.
With Wimbledon champion Andy Murray watching from the team box at the downtown outdoor Tasmajdan Stadium, his older bother Jamie teamed with Dom Inglot to beat Nenad Zimonjic and Filip Krajinovic 6-1 6-7 (2) 6-3 6-4.
In the decisive reverse singles on Sunday, Dusan Lajovic is scheduled to play Kyle Edmund, and Janko Tipsarevic to face James Ward.
Earlier, Lajovic breezed past Ward 6-1 6-3 6-2 to bring Serbia level 1-1.
Zimonjic, the 40-year-old veteran, dropped his serve twice with double-faults for key breaks in the first and third sets. The second was more damaging as it gave Britain a 5-3 lead and Inglot served out the third set with two consecutive aces.
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Zimonjic's partner, Krajinovic, playing his first Davis Cup doubles, then dropped his serve at the start of the fourth and the Britons never let the advantage slip.
The Drina March, a popular Serbian World War I marching tune, was played between every game and the Serbs had a break point with Inglot serving for the match.
But the Britons saved it, then the Serbs saved one match point when Krajinovic played a great lob. The Britons then got to replay a point because a public fan in the stands shouted "Out" on Inglot's serve and he hit a service winner to clinch the match.
The second singles could not be played on the opening day because of rain and was postponed until Saturday, when it also began an hour later than scheduled.
But the weather then cleared and Lajovic put Serbia back in the match. He won 10 straight points in breaking Ward at love and holding at love for a decisive 3-1 lead in the third set.
In the opening singles, Edmund beat Tipsarevic 6-3 6-4 6-0 on Friday.
Serbia is without top-ranked Novak Djokovic, while Britain is missing No. 2 Andy Murray.
The younger Murray, however, came to Belgrade to support the team from the sidelines, while Djokovic stayed away.
Lajovic broke serve in the opening game and that set the tone for the match.
"A tough start, he didn't do much wrong," Ward said. "It's one of the heaviest clay courts I've ever played on, it doesn't suit my game at all.
"It's not my ideal surface in slow and heavy conditions. He was just too good today."
Lajovic agreed about the condition of the clay court after heavy rains overnight.
"As soon as you put pressure on your foot, it falls apart," Lajovic said.
