Rousseff, in a radio interview, said steps were being taken to improve security in the 12 cities where matches are scheduled to be held from June 12 to July 13.
She insisted that fans, tourists, soccer teams and dignitaries expected to flock to Brazil for the World Cup play would be well protected.
"The federal police, the national public security force, the highway police -- all these organs are ready and positioned to act within their areas of competence," she said.
Brazilian cities have been hit since last June by often violent protests -- most recently one on February 6, in which a television cameraman was killed.
Rousseff said the vandalism that has often accompanied the protests were "inadmissible in a democratic country."
Her government is working on a bill that would toughen penalties for acts of vandalism during the World Cup, and the Brazilian Congress is debating a separate "anti-terrorist" bill that also would stiffen sanctions.