The 77-year-old Fifa president declares his discontent with the tournament's organisation, though he is confident that Brazilians will not "attack" the competition
Several venues - including the Sao Paulo Stadium, where two workers died in November - were not completed in time to meet Fifa's deadlines and Blatter is not impressed with the nation's preparations ahead of this summer's tournament.
"Brazil has now come to realise that they started too late," he was quoted as saying by 24 hours.
"They are the country who are the most delayed in terms of World Cup organisation since I have been at Fifa, even though they had such a long time [seven years] to prepare."
Last year's Confederations Cup in Brazil was marred by civilian protests against the costs of the World Cup but Blatter sees it as unlikely that this summer's tournament will come under threat.
"I am an optimist, not a pessimist," he remarked. "Football will be protected. I believe that Brazilians will not attack football directly. This is the sport's home, it's a religion.
"But we know there will be new demonstrations, protests. Last year, they were born of social networks. There was no goal but, at the World Cup, they will be more directed, more structured."
The World Cup is scheduled to kick off on June 12, with the final taking place on July 13.