The world number 13 edged Tsitsipas 6-7, 6-3, 6-3 to secure the fifth top-five win of his career.

Schwartzman’s victory came after Federico Delbonis put Argentina on track for a second Group D triumph with a 7-6, 6-1 win over Michail Pervolarakis.

Argentina completed a 3-0 success when Máximo González and Andrés Molteni downed Markos Kalovelonis and Petros Tsitsipas 6-3, 4-6, 11-9.

Poland's Hubert Hurkacz avoided a huge upset to lead his team to their second victory of the tournament in Group D.

Last year’s Miami Open champion dropped the first set to world number 571 Aleksandre Metreveli of Georgia before triumphing 6-7, 6-3, 6-1.

"He played well in the first set and things were not going my way, but I got better with each set and am happy to get the win," Hurkacz said.

Earlier, Kamil Majchrzak gave Poland a strong start when he thrashed Aleksandre Bakshi 6-1, 6-1 in just 53 minutes.

Poland rounded off a 3-0 victory over Georgia when Szymon Walkow and Jan Zielinski defeated Aleksandre Bakshi and Aleksandre Metreveli 6-7, 6-2, 10-6.

Roberto Bautista Agut proved too strong for Casper Ruud as he helped Spain overcome Norway in Group A.

The 33-year-old beat Ruud 6-4, 7-6 after Pablo Carreno Busta dismissed Viktor Durasovic 6-3, 6-3 in 69 minutes.

A 3-0 win was sealed when Alejandro Davidovich Fokina and Pedro Martínez swept aside Lukas Hellum Lilleengen and Andreja Petrovic 6-4, 6-1.

Chile and Serbia played out a Group A thriller with all three matches going down to a deciding set.

Filip Krajinović edged Alejandro Tabilo 6-4 3-6 7-6 to give Serbia the lead before Cristian Garin levelled the tie.

Garin was leading 4-6, 6-4, 3-0 when Dušan Lajović retired hurt after two hours and 14 minutes.

Tomas Barrios Vera and Alejandro Tabilo sealed victory for Chile with a 6-4, 3-6, 10-7 win over Nikola Ćaćić and Matej Sabanov.

Action continues tomorrow with Germany taking on the United States and Canada battling it out with Britain in Group C and Italy facing France and Russia meeting Australia in Group B.