The latest allegations of online snooping by the National Security Agency emerged Sunday night when TV Globo reported Brazilian oil giant Petrobras -- world leader in deep-water oil exploration -- was among those targeted, along with Google and the French foreign ministry.
Rousseff said in a statement that, "if the facts are confirmed, it would be clear the espionage was not for security or the fight against terrorism, but to respond to economic and strategic interests."
"Without doubt, Petrobras is not a threat to the security of any country," the president said.
These attempts to steal "data and information are incompatible with democratic co-existence between friends," she added, saying Brazil would "take all measures to protect the country, the government and its companies."
Petrobras said in a statement it has highly qualified and constantly updated systems to protect its internal communications network.
Brazil's foreign minister headed Monday to the Untied States where he is to meet this week with National Security Advisor Susan Rice over the spying row.
The meeting between Luiz Alberto Figueiredo and Rice is planned for Wednesday or Thursday in Washington, though the date has not been confirmed, a spokesman for the Brazilian foreign ministry told AFP.
Rousseff had expressed her "personal indignation" over the allegations of online snooping by the US National Security Agency during comments on the sidelines of the G20 summit last week in Russia.
The Brazilian leader had been scheduled to make a state visit October 23 to Washington, but Brasilia now says the trip depends on the US response to the spying allegations.
"The Brazilian government is determined to get clarification from the US government ... and require specific action to remove the possibility of espionage once and for all," Rousseff said Monday.
TV Globo reported Sunday a leaked US intelligence document highlighted Google, Petrobras, the French foreign ministry and SWIFT, a provider of secure financial messaging services to 10,000 banks and other financial institutions in 212 countries, as "targets" of the US online snooping.
The channel said it obtained the information from Glenn Greenwald, a blogger and columnist for the Guardian newspaper, who got secret files from former US intelligence contractor Edward Snowden.
US National Intelligence director James Clapper responded to the allegations in a statement, saying the US "collects foreign intelligence -- just as many other governments do -- to enhance the security of our citizens and protect our interests and those of our allies around the world."