The face of Edward Snowden appeared on a screen as he manoeuvred the wheeled android around a stage at a TED gathering, addressing an audience in Vancouver without ever leaving his secret hideaway.

"There are absolutely more revelations to come," he said. "Some of the most important reporting to be done is yet to come."

Snowden, a former National Security Agency contractor who has been charged in the United States with espionage, dismissed the public debate about whether he is a heroic whistleblower or a traitor.

Instead, he used the conference organised by educational non-profit organisation TED to call for people worldwide to fight for privacy and internet freedom.

Internet creator Tim Berners-Lee briefly joined Snowden's interview with TED curator Chris Anderson, and came down in the hero camp.

When Anderson posed the question to the TED audience, the idea that Snowden is a force for good met with applause.

"Hero patriot or traitor; I would say I am an American citizen just like anyone else," Snowden said. "What really matters here is the kind of government we want; the kind of internet we want."

He said he was inspired to pass a huge trove of NSA files to reporters when he saw US spying tactics going too far and intruding into the private data of millions of internet and telephone customers.

Snowden argued that if he had gone to the US Congress with his concerns, he would have risked being "buried along with the information".

Snowden instead urged the "adversarial press" to challenge government and ignite public debate "without putting national security at risk".