The leaks have reopened the post-Sept. 11 debate about privacy concerns versus heightened measure to protect against terrorist attacks, and led the NSA to ask the Justice Department to conduct a criminal investigation.
The Guardian said it was publishing the identity of Edward Snowden, a former technical assistant for the CIA and current employee of defense contractor Booz Allen Hamilton, at his own request.
"My sole motive is to inform the public as to that which is done in their name and that which is done against them," Snowden told the newspaper.
A spokesman for the Director of National Intelligence did not have immediate comment on the disclosure.
The NSA has been collecting the phone records of hundreds of millions of Americans each day, creating a database through which it can learn whether terror suspects have been in contact with people in the U.S. The NSA program does not listen to actual conversations.
Separately, an Internet scouring program, code-named PRISM, allows the NSA and FBI to tap directly into U.S. nine U.S. Internet companies to gather all Internet usage — audio, video, photographs, emails and searches. The effort is designed to detect suspicious behavior that begins overseas.
Director of National Intelligence James Clapper decried the revelation of the intelligence-gathering programs as reckless and said it has done "huge, grave damage." In recent days, he took the rare step of declassifying some details about them to respond to media reports about counterterrorism techniques employed by the government.
President Barack Obama, Clapper and others have said the programs are authorized by Congress and subject to strict supervision of a secret court.
"It's important to recognize that you can't have 100 percent security and also then have 100 percent privacy and zero inconvenience," Obama said. "We're going to have to make some choices as a society. And what I can say is that in evaluating these programs, they make a difference in our capacity to anticipate and prevent possible terrorist activity."
Snowden told the newspaper that he lacked a high school diploma and enlisted in the U.S. Army until he was discharged with broken legs after a training mission.
After leaving the Army, Snowden got his foot in the door with the NSA at a covert facility at the University of Maryland, working as a security guard.
He later went to work for the CIA as an information technology employee and by 2007 was stationed in Geneva, Switzerland, where he had access to classified documents.
During that time, he considered going public with what he knew about the nation's secretive programs. He decided against it, he told the newspaper, because he did not want to put anyone in danger and he hoped Obama's election would curtail some of the clandestine programs.
He said he was disappointed that Obama did not rein in the surveillance programs.
"Much of what I saw in Geneva really disillusioned me about how my government functions and what its impact is in the world," he said. "I realized that I was part of something that was doing far more harm than good."
Snowden left the CIA in 2009 to join a private contractor. He spent the last four years at the National Security Agency, the intelligence arm that monitors electronic communications, as a contractor with consulting giant Booz Allen Hamilton and, before that, Dell.
The Guardian reported that Snowden was working in an NSA office in Hawaii when he copied the last of the documents he planned to disclose and told supervisors that he needed to be away for a few weeks to receive treatment for epilepsy.
He left for Hong Kong on May 20 and has remained there since, according to the newspaper. Snowden is quoted as saying he chose that city because "they have a spirited commitment to free speech and the right of political dissent", and because he believed it was among the spots on the globe that could and would resist the dictates of the U.S. government.
"I feel satisfied that this was all worth it. I have no regrets," Snowden told the newspaper.
The newspaper said Snowden has been monitoring news coverage of the leaks and asked to be identified after several days of interviews.
"I have no intention of hiding who I am because I know I have done nothing wrong," Snowden is quoted as saying.
Officials said the revelations were dangerous and irresponsible. Rep. Mike Rogers, the Republican chairman of the House Intelligence Committee, said the journalists who disclosed the operations did not grasp the consequences.
"He doesn't have a clue how this thing works," Rogers told ABC's "This Week" on Sunday. "Neither did the person who released just enough information to literally be dangerous."
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