Off-field issues have raised questions as to the suitability of the South American nation as a host for football's biggest showpiece.
Four stadiums are still yet to be finished and three construction workers have been killed during the building of the Arena da Amazonia in Manaus.
FIFA put back their deadline of December for all stadiums to be finished and still the Arena da Baixada in Curitiba is not expected to be completed until the middle of May - just a month before the finals begin.
However, Blatter, the president of the world governing body, is confident the eagerly-awaited competition will be a resounding success as Brazil prepares to host the finals for the second time.
He told FIFA.com: "One hundred days is a long way to go and it's a short way. It's a short way to go if there are still problems, but now all problems are under control and it will be in 100 days an exceptional good start for an exceptional competition - FIFA's World Cup in Brazil, the country of football.
"They will receive this competition with open arms and full of their heart."
The hosts Brazil face Croatia in Sao Paulo in the curtain-raiser for the tournament on June 12.
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