Edward Snowden, the rogue US defence contractor, has offered to help Brazil investigate American spying programmes in exchange for being granted permanent political asylum.
In an open letter to the Brazilian people, Mr Snowden said he was willing to help their government "where appropriate and legal", but said that the US government would prevent him from acting unless he was granted asylum.
The former CIA contractor is in self-imposed exile in Russia, where he fled after disclosing the scope of the National Security Agency's spying programmes using stolen documents that he leaked to the 'Guardian' and the 'New York Times'.
It was revealed that the America government had intercepted communications by Dilma Rousseff, the Brazilian president, and had spied on Petrobras, the state-owned oil company.
In the letter published by 'Folha de Sao Paulo' newspaper, Mr Snowden said many Brazilian senators had "asked me to help with their investigations into suspected crimes against Brazilian citizens".
He added: "I've expressed my willingness to assist where it's appropriate and legal, but, unfortunately, the US government has been working hard to limit my ability to do so. Until a country grants me permanent political asylum, the US government will continue to interfere with my ability to speak out."
The White House this week ruled out any prospect of offering an amnesty to Mr Snowden after the idea was floated by a senior NSA officer in a television interview, with officials reiterating that the former contractor was a felon who should return to America to stand trial. The US remains under intense pressure over the Snowden leaks, which this week had their first visible legal impact when a court in Washington ruled that the bulk collection of telephone records the government kept was "Orwellian" and almost certainly unconstitutional.
The court's findings, which will be subject to appeal, were a blow to the White House which had instituted a presidential review of NSA practices to show that the administration was serious about addressing privacy issues.
The Snowden affair has also damaged White House relations with internet companies, including Yahoo! and Apple, which signed a letter last week calling for changes to US surveillance practices.
The CEOs met Barack Obama in the White House yesterday in a private meeting at which company representatives said they would press their case.
Mr Snowden originally said his biggest fear when leaking the NSA documents was that his message would be ignored, praising the response of Brazil to ensure that was not the case. "The reaction in certain countries has been especially inspiring to me, and Brazil is one of them, no doubt," he said.
The office of the Brazilian president has not publicly responded to the letter as there has been no formal application for asylum. (© Daily Telegraph, London)