Michael Llodra and Gael Monfils put France on the verge of the Davis Cup final when they won the opening rubbers of their semi-final against Argentina for a 2-nil lead.
Llodra served and volleyed his way to a 7-5 4-6 7-5 6-3 win over Juan Monaco before world number 15 Monfils saw off David Nalbandian 6-4 2-6 6-4 6-3.
The winner of this semi-final will take on either Serbia or the Czech Republic in December's final.
In that match-up, Serbia have drawn level with the Czechs at 1-1, shrugging off the shock withdrawal of world number two, Novak Djokovic.
Radek Stepanek gave the Czechs the lead, beating Djokovic's replacement Viktor Troicki 4-6 6-2 6-4 6-4.
But 37th-ranked Janko Tipsarevic then beat Wimbledon runner-up and world number seven, Tomas Berdych 7-5 6-2, 2-6 7-6 (7-5) to level the tie.
Djokovic, who was initially reported to have withdrawn due to stomach problems, said in a statement he was actually still tired after hard efforts at the US Open and the long trip overseas.
He hinted he was ready to return to play in the doubles, and reverse singles if necessary.
Serbia, who have never played in a Davis Cup final, reached this stage by defeating the United States 3-2 in Belgrade and then cruising past Croatia 4-1 in the quarter-finals in Split.