Edward Snowden has told supporters he would be willing to return to the US if the government could guarantee a fair trial.

The former National Security Agency contractor, who has been living in Russia since June 2013, said he would present a public interest defence of his decision to leak thousands of classified intelligence documents if he appeared before a US jury. “I’ve told the government I would return if they would guarantee a fair trial where I can make a public interest defence of why this was done and allow a jury to decide,” Snowden told a libertarian conference, the New Hampshire Liberty Forum.

Snowden, who was speaking via Google Hangouts, faces US charges under the Espionage Act that could land him in prison for up to 30 years.

In May 2013, Snowden flew to Hong Kong after leaving his job at an NSA facility in Hawaii. The following month he revealed thousands of classified NSA documents, and then travelled to Russia, where he was subsequently granted asylum.

The documents revealed the existence of mass surveillance programmes run by the NSA and British intelligence agency GCHQ, which involved the bulk interception of phonecalls and internet traffic.

Snowden has previously spoken of making offers to the government to return home and his willingness to discuss a plea deal and even go to jail. But in an interview on BBC Panorama last year, the whistleblower said the US justice department had made no effort to contact him.

Snowden’s revelations set off an international debate about the balance between security and privacy. Supporters hailed Snowden for exposing what they saw in some cases as an illegal invasion of privacy, while critics believed he hampered the security services’ ability to fight terrorism.