Daniel Nestor and Vasek Pospisil subdued Nenad Zimonjic and Ilija Bozoljac 6-7 (6-8), 6-4, 3-6, 7-6 (7-5), 10-8 in a rip-roaring doubles on Saturday to give Canada a 2-1 lead against 2010 winners Serbia in their Davis Cup semifinal.
Games went with serve in the final set until the tiring Zimonjic sliced a backhand into the net on his serve and Pospisil held in the final game of the four-hour, 20-minute contest.
Zimonjic and Bozoljac saved three set points to nose ahead in front of 8,000 vociferous fans in Belgrade's Kombank Arena, including several hundred flag-waving Canadian supporters.
Nestor, who won one French Open and two Wimbledon titles with Zimonjic before they split in 2010, engineered a break of his former partner's serve in the second set, which put Canada on level terms.
A delicious backhand down the middle from Bozoljac broke Nestor's serve in the sixth game of the third set, allowing Serbia to regain control of the match before Pospisil redressed the balance when he sealed the fourth set tie-break with an ace.
Bozoljac saved one match point on Pospisil's serve but was powerless to stop the second as the 22-year-old wrapped up the slugfest with a stinging forehand down the line.
Nestor was full of gratitude for Canada's travelling support. "They were amazing and we really appreciate the time and resources they sacrificed to come here for us," the 41-year old Belgrade-born doubles specialist told a news conference.
Tomas Berdych and Radek Stepanek put defending champions Czech Republic into the Davis Cup final by beating Argentina's Carlos Berlocq and Horacio Zeballos in the doubles on Saturday.
World No 5 Berdych and US Open doubles champion Stepanek defeated the Argentines 6-3, 6-4, 6-2 giving the Czechs an unassailable 3-0 lead in their semifinal and a place in their third final in five years.
The final is scheduled to be held from November 15-17.
The Czechs' all-time best doubles pairing with a 13-1 record were playing together for the first time this season and in front of a crowd of more than 11,000 at Prague's O2 Arena, where the team lifted the trophy for the first time as an independent nation last year.
Stepanek, coming into the competition on the back of winning the men's doubles title with Leander Paes at Flushing Meadows last weekend, immediately set his sights on another Davis Cup title.
Argentina went into the tie as underdogs and played without world number seven Juan Martin Del Potro, who sat out this year's competition, and their best doubles player, David Nalbandian, who underwent shoulder surgery in May.
The Czech pair, following up singles wins over Juan Monaco and Leonardo Mayer on Friday, showed their experience in the first set on Saturday, fighting off a break point to go up 4-3. They then broke the Argentines before serving out the set.
The second set played out similarly before the Czechs were able to break Berlocq's serve for the second time to go up 4-3. The Argentine pair got back to 5-4 but Berdych served well and finished off the set with a smash.
Berdych, the Czechs' top player, broke Zeballos in the third set to go up 3-2 when he fired a forehand winner from the baseline that made Berlocq step out of the way. The Czechs never looked back and Berdych sent the team through to the final.
Results: Semifinals: At Prague: Czech Republic lead Argentina 3-0 (On Saturday: Tomas Berdych/ Radek Stepanek bt Carlos Berlocq/ Horacio Zeballos 6-3, 6-4, 6-2)
At Belgrade: Serbia trail Canada 1-2 (On Saturday: Ilija Bozoljac/ Nenad Zimonjic lt to Daniel Nestor/ Vasek Pospisil 7-6 (8-6), 4-6, 6-3, 6-7 (5-7), 8-10).