Stadiums in Cuiaba and Curitiba appear unlikely to meet the December 31 deadline set ahead of next year's showpiece event.
In Cuiaba, seat installations are causing the delay, Curitiba is unlikely to be ready before February and the stadium in Sao Paulo, where two construction workers were killed, has also been delayed.
Blatter, who expressed his regret about the accident in Sao Paulo, said Brazil needed to be trusted to have the World Cup ready.
"We know that there is and we have just received the report there are some small delays in construction of stadia," Blatter said.
"But they are so small that with one exception we can just close our eyes and say everything will be ready.
"It is a question of trust and confidence when we go into an event like a FIFA World Cup.
"Here again I have to express our trust and confidence in the organisation here, in the state, central government and the different cities and the reports we have listened to today give us the security that we will go forward to a very positive one."
FIFA secretary general Jerome Valcke outlined the problems at Curitiba's Arena da Baixada, which is still three months from completion.
"The stadium is facing some problems but we organised ourselves to be ready to get the stadium at the end of February 2014 in order to install all the temporary facilities we need like IT and others," he said.
"It is important for us also to make sure that sooner than later we have a seating plan in order that we are selling tickets which correspond to a seat and not tickets which don't have a seat because we cannot do that as you can imagine."
Blatter said FIFA had no plans to change kick-off times despite concerns over high temperatures and humidity in parts of the country.
"We are sticking on the kick-off times," he said.
"They have been decided and confirmed, but not I would say official confirmation, but tomorrow with the executive committee we will do that, there is no change in the kick-off times."
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