Argentina's Juan Martin del Potro came from two sets down to beat Croatia's Marin Cilic as the 2016 Davis Cup final went to a deciding rubber in Zagreb.
Croatia looked set for the second title in their history when world number six Cilic won a first set tie-break then broke twice in the second.
Del Potro, the 2009 US Open champion, battled back to win 6-7 (4-7) 2-6 7-5 6-4 6-3 in four hours 53 minutes.
Argentina's Federico Delbonis plays Ivo Karlovic in Sunday's decider.