The president of the Spanish Footballers' Association (AFE) has said La Liga players will not play regular-season games in the United States.
On Tuesday, La Liga president Javier Tebas said plans to play Girona's home match against Barcelona in Miami on Jan. 26 were moving forward despite opposition.
The AFE has said it is against the game being played overseas, with the Royal Spanish Football Federation unlikely to authorise the move.
"We've said it 200 million times -- the players will not go to those games," Aganzo told reporters on Wednesday.
Asked about reports that Futbolistas ON, a union founded in April to represent Spanish professional footballers, had requested further information on the U.S. proposals, Aganzo said: "I was not aware of this.
"But we are the AFE, and we are very clear how we have to defend our colleagues -- and in the meeting that we had with the [team] captains, they made it very clear that they are the ones that decide."
Last month, FIFA voiced reservations over La Liga's plan, part of a 15-year marketing agreement with Relevent Sports to promote football in North America.