This month, Judge Richard J. Leon of Federal District Court for the District of Columbia said the N.S.A.'s mass collection of data was probably unconstitutional. President Obama appointed an advisory committee of outside experts to review the agency’s operations; it issued a report last week that recommended curbing the agency’s data collection.

Britain’s security services, which work closely with their American counterparts, have also been deeply embarrassed by the revelations, and one of Mr. Snowden’s more striking comments in the broadcast refers to “1984,” Orwell’s celebrated novel about a state controlled by an omnipresent Big Brother.

“Great Britain’s George Orwell warned us of the danger of this kind of information,” Mr. Snowden said. “The types of collection in the book — microphones and video cameras, TVs that watch us — are nothing compared to what we have available today. We have sensors in our pockets that track us everywhere we go.”

But he also argued that his actions had set off a debate that could help restore faith in those who regulate electronic communications. “The conversation occurring today will determine the amount of trust we can place both in the technology that surrounds us and the government that regulates it,” Mr. Snowden said. “Together, we can find a better balance, end mass surveillance and remind the government that if it really wants to know how we feel, asking is always cheaper than spying.”

Mr. Snowden has spoken out publicly before, and his latest comments are in line with others he made this week. In a lengthy interview with The Washington Post, he said he had achieved what he set out to do. “For me, in terms of personal satisfaction, the mission’s already accomplished,” he said. “I already won. As soon as the journalists were able to work, everything that I had been trying to do was validated. Because, remember, I didn’t want to change society. I wanted to give society a chance to determine if it should change itself.”