"With the power of Brazil, and I don't only speak of the economic power but also with the willpower, Brazil will be ready and will deliver a wonderful World Cup," Blatter told reporters at a news conference at FIFA headquarters on Tuesday.
"When there is one year or less to go before the World Cup, there is always the question of will they be ready. But they will be ready because it is the World Cup and nobody can afford not to be ready.
"There is no problem and I can say, definitely, don't be afraid. It's all a question of trust and confidence and trust and confidence from the FIFA side is totally there," added Blatter, seated alongside Brazil Sports minister Aldo Rebelo.
Brazil's preparations have been dogged by delays to stadiums and other infrastructure and deadlines have been repeatedly missed.
The famous Maracana stadium, which FIFA had demanded must be ready by last December for this year's Confederations Cup, will not be handed over until April 27.
Blatter said he was not concerned.
"I would never measure organising countries against the punctuality of Swiss trains," he added.
"We have a universal approach and we do not need this precision. The comparison does not work for me because I am a little more universal."
