As Brazil rushes to finish stadiums and deal with a wave of protests ahead of the June 12 kick-off, Rousseff partly blamed FIFA for the spiralling World Cup bill but said the money spent would leave a positive legacy.
The leftist leader, who is seeking reelection in October, said FIFA had assured Brazil that host stadiums would be built with private money.
But the government eventually realised private-sector investment would not even cover "half a stadium," and provided most of the financing itself, Rousseff told journalists at a dinner yesterday at the presidential residence in Brasilia.
But she insisted that the vast majority of public spending related to the tournament was "for Brazil" over the long-term and not limited to the World Cup.
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She said hosting the tournament had spurred many cities to undertake badly needed public transport projects - though she acknowledged many of them would not be completed before the World Cup.
The Brazilian government has faced a wave of protests over more than USD 11 billion it is spending on the tournament, money critics say should have been used to address urgent needs in areas such as education, health care and transport.
The protests turned violent at times, casting a shadow over the tournament and raising fears of a repeat this year.
Looking relaxed as she had dinner with journalists, Rousseff said protests would be allowed during the World Cup as long as they were peaceful and did not interfere with the event.
"We fully guarantee people's security," she said.
Brazil is still scrambling to finish five of the 12 host stadiums, including Sao Paulo's Corinthians Arena, which will host the opening match but still has not had all its seats installed.
But on the pitch, Brazil were looking ready for kick-off yesterday, routing Panama 4-0 in a friendly.