Snowden told The Washington Post in his first in-person interview since his June arrival in Russia, which granted him temporary asylum, that he was satisfied because the public is now informed about the US government's massive sweep of Internet and phone records.
"For me, in terms of personal satisfaction, the mission's already accomplished," he said in the the interview published Tuesday.
"I already won.
"As soon as the journalists were able to work, everything that I had been trying to do was validated," Snowden told the Post.
"Because, remember, I didn't want to change society. I wanted to give society a chance to determine if it should change itself."
The NSA's collection of communications data has grown dramatically since the September 11, 2001 attacks.
On Friday, President Barack Obama said he welcomed a debate about the NSA's role as he weighs possible changes to its broad powers amid a public outcry over rights to privacy. The president said he would make a "pretty definitive statement" in January about how the NSA should be overhauled.
A panel of legal and intelligence experts chosen by the White House has recommended curbing the agency's powers among 46 proposed changes, warning that its sweeps in the war on terror have gone too far.
And a federal judge has warned that the NSA's routine collection of nearly all Americans' phone records was probably unconstitutional.
Snowden was interviewed in Moscow by Barton Gellman, a Post reporter who has received leaks from the former NSA contractor. The leaker's first revelations were initially published by the Post and the Guardian in June.
"He was relaxed and animated over two days of nearly unbroken conversation, fueled by burgers, pasta, ice cream and Russian pastry," Gellman said of Snowden.
Federal prosecutors have filed a criminal complaint against Snowden, charging him with espionage and felony theft of government property.
But the 30-year-old said he was not being disloyal.
"I am not trying to bring down the NSA, I am working to improve the NSA," he said. "I am still working for the NSA right now. They are the only ones who don't realize it."
The leaker said it was lawmakers' decision to keep the NSA programs hidden and their failure to ask probing questions that entitled him to spill the secrets.
"The system failed comprehensively, and each level of oversight, each level of responsibility that should have addressed this, abdicated their responsibility," he said.
Snowden's revelations have outraged civil liberties advocates and even US allies, angered by reports that the United States was monitoring their leaders' cellphone calls and other virtual communications.