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In an interview with NBC, he reiterated that he had worked undercover overseas for the CIA and NSA.
He said the US got better intelligence from computers than human agents.
Mr Snowden, 30, fled the US in May 2013 and has been living under temporary asylum in Russia.
Among other things, the leaks detailed the NSA's practice of harvesting data on millions of telephone calls made in the US and around the world, and revealed the agency had snooped on foreign leaders.
The revelations have sparked a debate in the US over the appropriate role of the NSA and the extent to which it should be authorised to conduct such broad surveillance.
President Barack Obama has asked Congress to rein in the programme by barring the NSA from storing phone call data on its own and to require it to seek a court order to access telecom companies' records.
Last week, the US House passed such legislation, sending it to the US Senate.
In excerpts of an interview with NBC's Brian Williams, Mr Snowden said he had trained as a spy "in sort of the traditional sense of the word in that I lived and worked undercover overseas - pretending to work in a job that I'm not - and even being assigned a name that was not mine," BBC cites.
But he described himself as a technical expert who did not recruit agents.
"What I do is I put systems to work for the US," he said. "And I've done that at all levels from the bottom on the ground all the way to the top. Now, the government might deny these things, they might frame it in certain ways and say, 'Oh well, you know, he's - he's a low-level analyst.'"
But he said he had worked for the CIA and NSA undercover, overseas, and lectured at the Defense Intelligence Agency.
When Mr Snowden fled the US, he had been working as a technician for Booz Allen, a giant government contractor for the National Security Agency.