France were also well placed going into Saturday's doubles after Richard Gasquet clawed back a two-set deficit against Germany's Florian Mayer in Stuttgart as last year's runners-up also won both opening singles.
Spain, despite missing deposed world number one Rafael Nadal, took a commanding 2-0 lead over hosts the United States in Austin, Texas.
Serbia's clash with Sweden was something of a mismatch. Even with newly-crowned Wimbledon champion and world number one Novak Djokovic pulling out of the singles with a knee niggle, Serbia made short work of the lowly-ranked Swedes, who are without their powerhouse world number five Robin Soderling.
Viktor Troicki beat world number 297 Michael Ryderstedt 6-3, 6-1, 6-7, 7-5 before Janko Tipsarevic saw off Ervin Eleskovic in quick time when his opponent retired hurt with a knee injury trailing 6-2, 1-0.
Argentina began Friday already 2-0 ahead against Kazakhstan after their tie in Buenos Aires started a day earlier because of municipal elections on Sunday, and the South Americans took a decisive lead when Juan Ignacio Chela and Eduardo Schwank beat Evgeny Korolev and Yuriy Schukin in straight sets.
The performance of the day was from Frenchman Gasquet. He trailed by two sets against Mayer but hit back to win 4-6, 4-6, 7-5, 6-3, 6-3 before Gael Monfils then beat Philipp Kohlschreiber 7-6, 7-6, 6-4.
In Austin, Feliciano Lopez gave Spain a winning start when he battled past American Mardy Fish 6-4, 3-6, 6-3, 6-7, 8-6 before world number six David Ferrer followed suit with a gutsy 7-6, 7-5, 6-3 victory over hometown favourite Andy Roddick.
