Edward Snowden, the former contractor for the National Security Agency who leaked classified documents regarding the agency's surveillance programs, has very sensitive "blueprints" describing how the agency operates, a journalist close to the story told The Associated Press.

Snowden has "literally thousands of documents" that constitute "basically the instruction manual for how the NSA is built" that could aid in duplicating or evading NSA surveillance tactics, The Guardian's Glenn Greenwald told the news agency on Sunday.

"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," Greenwald said, who noted that he had last communicated with Snowden about four hours before the interview.

The NSA whistleblower's leaks last month led to the public learning that the U.S. government has been working to spy on people via metadata from Internet companies and cellular records in two programs. The NSA and the Obama administration have said the goals of the surveillance programs were to track down foreign terrorists and terrorist threats.

Since the leak, the U.S. government has revoked Snowden's passport and is working to extradite him back to the U.S. Meanwhile, Snowden remains at the Moscow airport just outside Russia's customs area, effectively leaving him outside the legal auspices of the country.

Greenwald said the NSA "blueprints" don't represent a threat to U.S. national security, but could be embarrassing to the government.

"I think it would be harmful to the U.S. government, as they perceive their own interests, if the details of those programs were revealed," Greenwald told the AP.

Greenwald also addressed reports that Snowden had created a so-called dead man's pact that would trigger the release of a trove of documents if something were to happen to him.

"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."

Snowden, who reportedly has received asylum offers from Bolivia, Nicaragua, and Venezuela, said he was not willing to idly stand by while the NSA's massive eavesdropping apparatus was being turned inward on fellow citizens. The U.S. government has charged Snowden, 30, with espionage, theft, and conversion of government property.