Serbia and defending champions the Czech Republic were tied 1-1 after the first day of the Davis Cup final on Friday as Novak Djokovic and Tomas Berdych swept through in straight sets.
Djokovic, the world number two and recently-crowned ATP World Tour Finals champion, first beat 44th-ranked veteran Radek Stepanek, 7-5, 6-1, 6-4, in two hours and 10 minutes.
Seventh-ranked Berdych then put the Czechs level with a three-set win over 117th-ranked Dusan Lajovic -- 6-3, 6-4, 6-3 in an hour and 54 minutes.
In front of a frantic crowd in the sold-out Belgrade Arena sitting 15,500 people, Djokovic relied on a solid serve throughout the rubber.
He first broke Stepanek's serve in game six of the first set.
But then he found himself under heavy pressure, allowing the 34-year-old Czech to win seven straight points and take the serve back.
Djokovic showed some frustration before breaking Stepanek again for a 7-5 first-set win.
Stepanek earned three break points early in the second set, but Djokovic held on to his serve and embarked on a spree to take the set, 6-1.
A single break in game nine was all Djokovic needed in the third set to finish off Stepanek.
"I am happy with the way I played. Of course I was nervous at the beginning but it was very important for us to win the first set and then I relaxed," said Djokovic.
"I served well in the important moments."
Stepanek said he would have been happier had he won the rubber, before praising Djokovic's defence.
"I tried to dictate the pace, get him into difficult situations, but he got out of them," Stepanek said.
"I gave him quite a lot of trouble in sets one and three. I failed to earn a point (by winning the rubber), but it was great tennis," he added.
In the second rubber, the 23-year-old Lajovic offered some resistance, but the 28-year-old Berdych controlled the clash, earning a break apiece in each set.
Lajovic has replaced Janko Tipsarevic, the world number 36, who has been ruled out with a heel injury.
Serbia are also missing 76th-ranked Viktor Troicki due to a doping ban, while the Czechs have an interim captain for the final tie -- Vladimir Safarik, who replaced Jaroslav Navratil who was hospitalised with a pulmonary embolism.
In Saturday's doubles, Serbia's Ilija Bozoljac and Nenad Zimonjic are due to face the Czech Republic's Jan Hajek and Lukas Rosol.
But the Czechs are almost certain to bet on Berdych and Stepanek for the doubles too as the pair have lost only one of their 14 Davis Cup rubbers together since teaming up in 2007.
Serbia won their only Davis Cup title in 2010, beating France 3-2 in Belgrade.
The Czechs, playing their third final in five years, lifted the trophy last year after downing Spain 3-2 in Prague.
Previously, Czechoslovakia, which split into the Czech Republic and Slovakia in 1993, won the title in 1980.