Brazil says it is not considering granting asylum to Edward Snowden even after the former U.S. National Security Agency contractor offered on Tuesday to help investigate revelations that the NSA has spied on Brazilians and their president.
The Brazilian government has received no official request from Snowden since he arrived in Moscow in June, a foreign ministry spokesman said.
Without a formal request, asylum will not be considered, the spokesman said.
In a letter published Tuesday by the Folha de S. Paulo, a Brazilian newspaper, and by social media, Snowden offered to collaborate with a Brazilian investigation into the NSA Internet surveillance program he revealed earlier this year.
Simultaneously, Avaaz, a website for public petitions, launched an online signature campaign to press President Dilma Rousseff to grant Snowden asylum.
In his "Open Letter to the Brazilian People," Snowden said he would like to assist in a congressional probe into NSA's program, which monitored the personal communications of Rousseff and other Brazilians.
"I have expressed my willingness to assist wherever appropriate and lawful, but unfortunately the United States government has worked very hard to limit my ability to do so," the letter said.
Snowden is living in Russia under temporary asylum that is due to expire in August. He had previously asked for asylum in Brazil, among other countries, but Brasilia did not answer his request.
While Snowden stopped short of asking for asylum again in the letter, he suggested that any collaboration with Brazilian authorities would depend on it.
"Until a country grants permanent political asylum, the U.S. government will continue to interfere with my ability to speak," Snowden wrote.
The revelations of NSA spying damaged relations between the United States and Latin America's largest country and prompted Rousseff to cancel a state visit to Washington in October.
The spying also led Rousseff to become a global advocate for curbs on Internet surveillance.
Evidence that the NSA monitored Rousseff's email and cellphone, and hacked into the computing network of state-run oil company Petrobras, angered Brazilians and led the Senate to probe the extent of U.S. spying in Brazil.
Some members of Brazil's Congress have asked Russia for permission to interview Snowden but have received no reply, a congressional aide said.
In a Twitter message, Senator Ricardo Ferraço, chairman of the Senate foreign relations committee, said "Brazil should not miss the opportunity to grant asylum to Edward Snowden, who was key to unravelling the U.S. espionage system."
"The Brazilian government should grant him asylum and the U.S. government must understand that the NSA violated rights protected in Brazil's Constitution," fellow committee member Senator Eduardo Suplicy said.
The original English version of Snowden's letter was published on the Facebook page of David Miranda, partner of journalist and blogger Glenn Greenwald, who first brought the Snowden leaks to the world's attention.
Miranda started the petition on the Avaaz site for Brazil to offer the "courageous" Snowden asylum.
In his letter, Snowden praised Brazil's efforts at the United Nations to limit excessive electronic surveillance.
Last month a U.N. General Assembly committee expressed concern at the harm such scrutiny, including spying in foreign states and the mass collection of personal data, might have on human rights, following a joint resolution introduced by Brazil and Germany.
On Monday, White House spokesman Jay Carney dismissed the suggestion that the United States could grant amnesty to Snowden if he were to turn over the documents in his possession.