Sky News quoted Assange, as saying that the American legal action "had yet to be confirmed" but was "extremely serious".
"We have heard today from one of my US lawyers that there may be a US indictment for espionage for me coming from a secret grand jury investigation. There are obviously serious attempts to take down the content by taking us down as an organisation and take me down as an individual," he added.
Earlier, Attorney General Eric H. Holder Jr. had said that the Justice Department and Pentagon are conducting "an active, ongoing criminal investigation.'
On being asked how the United States could prosecute Assange, who is an Australian citizen, Holder had said: "Let me be very clear, it is not saber rattling. To the extent there are gaps in our laws. We will move to close those gaps, which is not to say . . . that anybody at this point, because of their citizenship or their residence, is not a target or a subject of an investigation that's ongoing." (ANI)