Spaniards Nicolas Almagro and Tommy Robredo will meet in the Buenos Aires Open semi-finals having won their rain-delayed quarter-finals on Saturday.
Sixth seed Robredo, in good form on the Latin American claycourt circuit, beat home favourite David Nalbandian 6-4 6-4 on Centre Court, while top seed Almagro won 7-5 6-3 against Argentine wild card Jose Acasuso.
Second seeded Swiss Stanislas Wawrinka, in his first tournament on clay since last year's French Open, beat Argentine 2007 champion Juan Monaco 7-5 6-3 on Court 2 and will meet eighth seed Juan Ignacio Chela in the other semi-final.
Chela made sure one Argentine reached the last four when he completed a 6-4 3-6 6-3 win over fourth seed Albert Montanes of Spain to reach his third semi-final at the Buenos Aires Lawn Tennis Club. The pair were locked at 3-3 in the third set of the only quarter-final to start on Friday before the rain.
The semi-finals were scheduled for Saturday night on Centre Court starting at 2230 GMT.
Robredo, in a clash of former champions, broke Nalbandian at the same stage in both sets to secure his win.
"I had two very good games at 4-4 in both sets and that's what gave me the victory," Robredo told a television reporter on Centre Court.
"(Nalbandian) is one of those players who mark a standard. To beat him shows I'm in a period of confidence."
Almagro had to work hard to beat former world number 20 Acasuso, now ranked 256, who was playing in his first ATP tournament since 2009 having lost last year to a knee injury.
"It was a hard match. 'Chucho' (Acasuso) is very keen to show the player he once was," world number 13 Almagro said, adding he was pleased with his own form.
"I've practically not dropped below semis (this year). I'm working well and very happy (with my game)," said Almagro, whose record this year is 12 wins in 14 matches.
Robredo and Almagro have won the first two tournaments on the circuit so far, Robredo the Santiago Open and Almagro last week's Brazil Open. The fourth tournament is the Mexican Open in Acapulco starting on Monday.