Lopez had just two service breaks in his 4-6, 7-6 (7-2), 7-6 (7-4), 6-4 win over Juan Martin del Potro. David Nalbandian had put Argentina ahead with a solid 6-3, 6-2, 6-3 victory over David Ferrer to start the indoor hard-court series.

The Lopez-del Potro match was tight until the fourth set. There was just one break in the first three sets, that coming in the first set by del Potro. Lopez cashed in the two tiebreakers and finally was able to break del Porto's serve early in the fourth set. While del Potro broke back, Lopez got another break and then held serve out for the match.

Nalbandian was the aggressor throughout his match, piling up 54 winners against 27 unforced errors. He had seven aces.

Spain's Lopez and Fernando Verdasco are to meet Argentines Jose Acasuso and Agustin Calleri, with the winner putting his country one match win away from the title.

Sunday's reverse singles have Ferrer facing del Potro and Nalbandian going against Lopez.

Argentina, 13-0 at home in Davis Cup series, has never won a Davis Cup title. Spain is looking for its third crown.