Former U.S. Open champion Juan Martin del Potro and former Wimbledon runner-up Tomas Berdych posted singles wins Friday, as host Argentina and the Czech Republic are tied at 1-1 in their best-of-five Davis Cup semifinal.

In the opening rubber, the 6-foot-6 del Potro, playing with a sore left wrist, handled Czech veteran Radek Stepanek 6-4, 6-4, 6-2, while Day 1's dramatic nightcap saw Berdych outlast Argentine Juan Monaco in five sets, 6-1, 4-6, 1-6, 6-4, 6-4, to level the showdown on the red clay at Parque Roca in Buenos Aires.

Berdych, who was a U.S. Open semifinalist last week, needed just over four hours to overcome the gritty Monaco. The sloppy match featured a whopping 21 breaks of serve, including 11 for the Czech winner.

The powerful Berdych prevailed despite committing 18 more unforced errors than Monaco (66-48).

Del Potro, meanwhile, smacked seven aces and was broken only once while piling up five breaks against the overmatched Stepanek. "DelPo" saved seven-of-eight break-point chances against him.

Saturday's pivotal doubles rubber will pit Argentines Carlos Berlocq and Eduardo Schwank versus a Czech tandem of Ivo Minar and Lukas Rosol, while Sunday's reverse singles currently call for the world No. 8 del Potro to lock horns with the sixth-ranked Berdych and the No. 11 Monaco to take on the 40th-ranked Stepanek.

The Argentines are captained by Martin Jaite, while the Czechs are led by Jaroslav Navratil.

The Czechs are 3-1 all-time versus the Argentines, including a win in their last meeting in a quarterfinal in Ostrava in 2009.

Argentina lost to Spain in last year's World Group final in Seville, falling to 0-4 in Davis Cup finals.

The Argentina-Czech Republic winner will meet the Spain-United States victor in the final in November.