Snowden has "blueprints" detailing how the US National Security Agency operates

former NSA analyst Edward Snowden

Glenn Greenwald, the columnist with The Guardian newspaper who communicates with the former NSA systems analyst Edward Snowden, and first reported on his intelligence leaks, told The Associated Press that  Snowden has "thousands of documents" that are "basically the instruction manual for how the NSA is built."

In an interview in Brazil, Greenwald said that, "In order to take documents with him that proved that what he was saying was true he had to take ones that included very sensitive, detailed blueprints of how the NSA does what they do," adding that the interview was taking place about four hours after his last communication with Snowden.

Snowden said he was not willing stand by while the NSA's massive eavesdropping apparatus was being turned inward on fellow citizens. He is believed to be stuck in the transit area of Moscow's main international airport, having arrived from Hong Kong on June 23. He has been offered asylum from Venezuela, Nicaragua and Bolivia, but traveling to those countries is complicated because the US has revoked his U.S. passport.

He has also received a conditional offer of asylum from Russian president Vladimir Putin, if Snowden desists from leaking information damaging to the United States. Snowden recently requested asylum from Russia but it is not clear whether Russia would honor his latest request for asylum,  because it could damage U.S.-Russia relations.

Regarding reports that Snowden had created a so-called dead man's pact that would trigger the release of documents if something were to happen to Snowden, Greenwald said: 

"It's not just a matter of, if he dies, things get released, it's more nuanced than that," he said. "It's really just a way to protect himself against extremely rogue behavior on the part of the United States, by which I mean violent actions toward him, designed to end his life, and it's just a way to ensure that nobody feels incentivized to do that."

Greenwald said he himself has beefed up his own security, particularly since a laptop went missing from his Rio home.