Kristina Mladenovic prevailed over CoCo Vandeweghe after fighting back from a set down to bring France level with defending Fed Cup champions United States in Aix en-Provence.
Earlier, in the other semi-final, the Czech Republic claimed a healthy 2-0 lead over Germany after dominant performances from Petra Kvitova and Karolina Pliskova.
Vandeweghe, who was unbeaten in 13 Fed Cup rubbers, stormed to the first set in 30 minutes but Mladenovic secured double breaks in the following two sets to earn a 1-6 6-3 6-2 victory and level their semi-final tie at 1-1.
“Extremely difficult start at 6-1 down,” said the 24-year-old Mladenovic.
“I was just hanging in there, fighting and mixing it up, trying to be aggressive before her, which is not easy.”
Mladenovic enjoyed a surge of success in the second set with an excellent slice drop shot to run into a 3-0 lead in 13 minutes. Vandeweghe broke back to level the scores at 3-3 before a searing forehand from the Frenchwoman helped her to break again and force a deciding set.
Mladenovic used her momentum to earn a double break on Vandeweghe’s serve with a string of winners that allowed her to serve out the match.
“I am happy we are equal tonight and ready for some more fights tomorrow,” Mladenovic added.
“I am not afraid at all. I am super pumped. I am here to defend and represent my country the best I can and we will continue fighting.”
Mladenovic will face Sloane Stephens in the opening rubber on Sunday.
Stephens, the 25-year-old US Open champion, also came through a tough opening match with France’s Pauline Parmentier as she fought from 5-1 down in the opening set to win 7-6 7-5.
“I didn’t play my best tennis but all I could do was fight back, keep the balls in the court and play for every point with my best effort,” Stephens said.
The United States or France look set to face the Czechs in the Fed Cup final with them needing just one more win in Stuttgart.
Kvitova claimed a comprehensive 6-3 6-2 victory over Julia Gorges before Pliskova prevailed over Angelique Kerber in a 7-5 6-3 win.
“I was very happy with my game today,” Pliskova said.
“My serve was great. Playing against Angie is always tough, and especially in Germany, so it was an important win for me.”
