NSA leaker Edward Snowden is sounding out Brazil as a possible refuge from U.S. prosecution, offering to help that country investigate the agency's espionage activities after published reports derived from his stolen documents soured U.S.-Brazil relations.

Snowden's offer came in the form of "an open letter to the people of Brazil" published today in the Folha de Sao Paulo newspaper. He's currently living under temporary asylum in Russia, but wrote: "Until a country grants permanent political asylum, the US government will continue to interfere with my ability to speak."

The letter was published a day after the White House rejected the suggestion Snowden would get amnesty if he cooperated with authorities to stem the damage from his leaks to the media.

"Mr. Snowden has been accused of leaking classified information, and he faces felony charges here in the United States. He should be returned to the United States as soon as possible where he will be accorded full due process and protections in our system. So that's our position and it has not changed," White House spokesman Jay Carney said.

Carney was reacting to a suggestion aired Sunday on CBS' "60 Minutes" by NSA investigator Rick Ledgett, who said the estimated 1.7 million documents stolen by Snowden contained "the keys to the kingdom," and it would be worth giving him asylum to secure the information they contain.

Brazilian officials ignored the request by Snowden, viewing his open letter as a bid to test the government's reaction, the Estado de Sao Paulo newspaper reported. President Dilma Rousseff was expected to meet later today with Foreign Minister Luiz Alberto Figueiredo to craft a response. The Brazilian government did not reply to a previous request for asylum by Snowden in July to avoid exacerbating problems with the U.S. over the issue, the paper said.

It's possible Rousseff may be favorable to the idea of giving Snowden refuge. She faces re-election in 2014, and domestic outrage over revelations that the NSA not only spied on her, but also on the state-controlled oil company Petrobras, has been a welcome distraction from other concerns and has raised her profile as an international leader on the subject of online privacy.

Snowden's leaks already have caused significant damage to U.S.-Brazil relations. Rousseff canceled a state visit scheduled for October, saying President Obama's reaction to her concerns was insufficient, and blasted the NSA's activities as a violation of international law in a speech to the U.N. General Assembly in September.