NSA deputy director Richard Ledgett on Thursday spoke out against former intelligence contractor Edward Snowden, saying he does a disservice to whistle blowers.

Ledgett took aim at Snowden in a hastily arranged video-link to a prestigious TED conference where Snowden had appeared in similar fashion two days earlier.

"We didn't realize that he was going to show up, so kudos to you guys for arranging a nice surprise like that," Ledgett said, kicking off a video chat with TED curator Chris Anderson.

Former intelligence contractor Snowden emerged from his Russian exile Tuesday in the form of a remotely-controlled robot to promise more sensational revelations about US spying programs.

The fugitive's face appeared on a screen as he maneuvered the wheeled android around a stage at the 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, sparked a debate here whether he is a traitor or a heroic whistleblower.

Ledgett said he wanted to weigh in at TED with the NSA perspective since Snowden has mixed "kernels of truth" with misleading information.

Snowden had alternatives to leaking NSA secrets and fleeing the country, according to Ledgett.

Snowden could have run his concerns up the chain of command; to any of an array of attorneys general, or to Congressional committees, Ledgett reasoned.

"He absolutely did have alternatives," Ledgett said.

"I think that characterizing him as a whistleblower hurts legitimate whistle-blowing activities."

Snowden used the conference organized by educational non-profit organization TED ("Technology Entertainment Design"), to call for people worldwide to fight for privacy and Internet freedom.

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."