The founder of Lavabit, the encrypted email service used by NSA whistleblower Edward Snowden, has said he's not planning to relaunch it from outside the US.

"I don't think I can continue to run Lavabit abroad as an American citizen. I would have to move abroad, effectively, to administer the service," said Ladar Levison in an interview with news site Democracy Now.

"As an American citizen, I'm still subject to the laws and jurisdiction of the United States, particularly as long as I continue to live here."

Levison – accompanied by his lawyer during the video interview – said he is legally unable to talk about the full circumstances of his decision to shut down Lavabit, which had 410,000 registered users when it closed last week.

"I can't talk about that. I would like to, believe me. I think if the American public knew what our government was doing, they wouldn't be allowed to do it any more," said Levison, who described the closure as "the lesser of two evils".

"There's information that I can't even share with my lawyer, let alone with the American public. So if we're talking about secrecy, you know, it's really been taken to the extreme," he said.

"It was a very difficult decision. But I felt that in the end I had to pick between the lesser of two evils and that shutting down the service, if it was no longer secure, was the better option."

Lavabit is one of two US-based encrypted email services to have shut down abruptly this month, with Silent Circle also having closed its Silent Mail service "to prevent spying".

In his original blog post announcing the Lavabit shutdown, Levison said his company was already "preparing the paperwork" for a legal challenge in order to "resurrect Lavabit as an American company".

In the Democracy Now interview, Levison expresses the desire for the US Congress to "act and change the laws that put me in this circumstance to begin with", warning that the impact will be felt well beyond the encrypted-emails industry.

"There's a real need in this country to establish what the rights are of our cloud providers, and unless we take actions to ensure that we can continue to operate secure, private services, I think we're going to lose a lot of business over the next few years," he said.

Canadian service Hushmail, Switzerland-based Neomailbox and Swedish firm Countermail are among the non-US services available as alternatives to Lavabit and Silent Circle.

Meanwhile, Mega – the new company of Megaupload founder Kim Dotcom – has said it is working on secure email and voice services in the hope of "making true crypto work for the masses".