World number one Novak Djokovic helped Serbia to a win over Austria, while Spain and Italy also enjoyed opening wins.
Dusan Lajovic squeezed past Gerald Melzer in a tough tie, winning 7-6(7-5) 3-6 7-5, and then Djokovic faced off against Dennis Novak, winning 6-3 6-2.
The doubles match saw Nikola Cacic and Filip Krajinovic take on Oliver Marach and Philipp Oswald with the Serbians winning in three sets.
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The US lost 2-1 to Italy in the countries’ opening Group E match.
The Italian Lorenzo Sonego beat Reilly Opelka in two sets, winning 6-3 7-6(7-4) in the tie’s first match.
The experienced John Isner could do little to hold off another emerging Italian contender, with Jannik Sinner easing past him 6-2 6-0.
In the doubles match, Rajeev Ram and Jack Sock teamed up to down Fabio Fognini and Lorenzo Musetti 7-6(7-5) 6-2 to secure a match.
Spain defeated Ecuador in their tie as late replacement Feliciano Lopez downed Roberto Quiroz 6-3 6-3. That was followed up by a win for Spain as Pablo Carreno Busta defeated Emilio Gomez 5-7 6-3 7-6(7-5).

Djokovic cruises past Novak to secure tie for Serbia against Austria

"I am very happy because it was an important victory," Carreno Busta said. "We now lead 2-0 and have the win. It is very important for the confidence and for the rhythm. In the second set and third set I felt more comfortable than in the first set. I had to continue fighting until the end because he played really well."
Busta and Marcel Granollers would take on Gonzalo Escobar and Diego Hidalgo in the last doubles match of the day.

Carreno Busta hits back to beat Gomez

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