Blatter's revelation earlier this year that FIFA had contingency plans should the country be deemed ill-prepared had triggered a flurry of speculation about possible alternatives.
With less than 18 months left before the tournament kickoff, the FIFA boss insisted South Africa would be ready to become the continent's first World Cup hosts.
"There is no Plan B, C or D -- for those who still have doubts, I tell you the 2010 World Cup will be organised in South Africa," Blatter told reporters in Tokyo.
"I will be proud because it is a little bit like my baby. I've had a dream for 34 years to bring the World Cup to Africa. It's a little bit like my baby."
The readiness of South Africa's stadiums and infrastructure have come under scrutiny but organisers promised they would be up to standard and on time.
"All the stadiums will be there," said the country's organising chief Danny Jordaan. "There will be a transport revolution. There's no question, we will be ready."
FIFA and South African organisers also sought to calm security fears after one Japanese journalist asked if it would be safe to leave his hotel at night during the World Cup.
'KILLING FIELD'
The country has one of the highest murder rates in the world and was last month described as a "killing field" by its own Safety and Security Minister Nathi Mthethwa.
"It would be a very strange World Cup if people stayed in their hotel rooms," said Jordaan. "Give me your number -- I will take you out for dinner."
Despite Jordaan's attempts to defuse concerns over South Africa's high crime rate, he was pressed to give details of the country's policing plans for 2010.
"There is extra investment and there will be 41,000 additional policemen," he said. "We will have helicopters and surveillance cameras."
The South African government has already pledged to spend more than $115 million to beef up security for the tournament.
While promising "blanket security" for World Cup venues, Jordaan said last month's militant attacks in Mumbai had not forced a rethink of South Africa's safety plans.
"I don't think South Africa is high on the list of targets (for an attack). We recognise it's possible but our police are working closely with Interpol," he said.
FIFA denied that the global financial crisis could spell trouble for the World Cup with TV and sponsorship deals almost completed and 75 percent of funds already in the bank.
"We are very safe," said FIFA general secretary Jerome Valcke. "Most of the companies, Hyundai, Coca-Cola and Sony, I would say are safe."
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