Piazon, currently on loan at Dutch side Vitesse Arnhem, has represented Brazil at both under-15 and under-17 levels.
But the 20-year-old's family have Italian passports and he recently turned down an approach by the Italian FA to switch allegiances as he believes he is much too young to decide his international future.
When asked about the proposal to play for Italy, Piazon told ESPN Brazil: "They sounded out my father and my agent, but I said not now.
"I need to wait for now, I don't have to take a decision like this when I am 20 years old.
"Maybe in the future, if I don't have any chance (with Brazil), and they come to me again, I might even consider the idea, but this is not what I have in mind at the moment."
Meanwhile, 18-year-old Pereira says he now wants to represent Brazil in the future, rather than Belgium, for whom he was capped at under-17 level.
He told Terra: "I told Belgium that I don't want to play anymore as I want to focus on Manchester United. They call me, but I want to play for Brazil.
"Brazil's U20 national team manager (Alexandre) Gallo came here, he said that he is seeing several Europe-based players and he told me that I am doing a good job and asked me to keep doing it this way.
"Let's see if I'll be called up more ahead, I hope it happens."
He added: "It's a dream to play for Brazil, I played for Belgium for three or four years, but it's not the same thing.
"I didn't feel at home, I support Brazil and Brazil is the best team in the world."