Football's governing body raised concerns about transport after the Confederations Cup last June but Blatter said it was time to have faith that the month-long tournament starting in June would be a success.
"South Africa is a tourist country that welcomes 11 million visitors a year so I don't know why there are doubts when it comes to football," he said at a news conference after meeting Spanish Prime Minister Jose Luis Rodriguez Zapatero in Madrid.
"The issue (of transport) will be definitively resolved for the World Cup," he added, speaking in Spanish.
South Africa lacks the extensive, efficient rail service that made travel easy at the last World Cup in Germany in 2006 but has built a network of new roads.
Part of a high-speed rail link around Johannesburg and Pretoria called the Gautrain may be ready in time to ferry World Cup visitors from Johannesburg airport into the city.
Fans are expected to use the mass transit service to reach stadiums and organisers have said 200 additional planes and a thousand new buses will be mobilised.
FIFA have also established a complex plan to bus and fly fans from big accommodation centres to small venues such as Polokwane on match days.
Blatter pointed to the Confederations Cup as evidence South Africa was ready to stage the much larger World Cup.
"Let's have confidence in Africa and let's end the doubts and go there together with the best players," he said.
"It's justice for Africa which has given a great deal to international football."
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