Iran trounced the U.S. 8-0 in Group C at the Arena Amadeu Teixeira in Manus, Brazil.
Mohammad Kashavarz, Ali-Asghar Hassanzadeh, Vahid Shamsaei and Hossein Tayebi each scored two goals for Iran.
Iran will play Uruguay on Tuesday while Belgium face the U.S.
“I am satisfied with the way my players played. Now, we are going to beat Uruguay in our last match in the group stage,” Iran futsal coach Ali Sanei said.
All four teams in the group advance to an additional stage, with placement matches determining the teams finishing first through sixteenth.
The Grand Prix de Futsal is an international futsal competition of the same kind as the FIFA Futsal World Cup but with invited nations and held annually in Brazil. It was first held in 2005.
Qualifying for the Futsal World Cup begins next year, and the tournament itself will be held in Thailand from Nov. 2-18, 2012.