Belgium took a 2-0 winning lead over Spain on Saturday to reach the Fed Cup final.
Justine Henin launched an astonishing comeback to beat Conchita Martinez in the opening singles of the decisive group B clash, recovering from 5-1 down in the final set to win 6-3 5-7 7-5.
Kim Clijsters then ensured there could be no way back for Spain by blasting Arantxa Sanchez-Vicario off court with a 6-1 6-2 victory.
Belgium face Russia in Sunday's final.