Vicente del Bosque's side enters the tournament as the reigning champion and won back-to-back European Championships in 2008 and 2012.
The Selecao overcame Spain 3-0 in last summer's Confederations Cup but the 73-year-old is still wary of the world champions and has grave concerns about Brazil's front line.
"The most important thing for Brazil is that they don't meet Spain," he told GQ.
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"They're a fantastic team to watch, are very organized and don't have a weak point. The only good thing about Spain from our perspective is that they play a clean game.
"They like to play and allow the other side to play and that's important for a team like Brazil. Spain are a side who play modern football.
"The Spanish have the same way of finding space and playing the ball.
"In the run up to World Cups, Brazil had had an attack which was the best in the world, although there were always comments that the defense wasn't was as good.
"This year, however, we have a team that who are very good from the middle of the pitch backwards but we need to sort out our front line."
Pele also admitted that he would have preferred Spain international Thiago Alcantara - born to Brazilian parents - to have chosen to represent Luiz Felipe Scolari's side.
"He would have been particularly good for us. I would have liked to have him in my team," Pele added.