The WikiLeaks founder, Julian Assange, has called on the world to "step forward and stand with" Edward Snowden, after the NSA whistleblower was charged with espionage by US federal prosecutors.

According to a statement on the WikiLeaks website, Assange said: "A few weeks ago, Edward Snowden blew the whistle on an ongoing program – involving the Obama administration, the intelligence community and the internet services giants – to spy on everyone in the world. As if by clockwork, he has been charged with espionage by the Obama administration."

It was revealed on Friday that the US has charged Snowden with unauthorised communication of national defence information and wilful communication of classified communications intelligence to an unauthorised person – charges that are part of the US Espionage Act. The 30-year-old, who is reportedly hiding in Hong Kong, has also been charged with theft of government property. The Washington Post reported that US authorities have asked Hong Kong to detain him on a provisional arrest warrant with a view to extradition.

It is just over a year since Assange sought refuge in the Ecuadorian embassy in London in order to avoid being extradited to Sweden, where he is wanted for questioning over allegations of rape and sexual assault. He claims the allegations are politically motivated.

In the statement, Assange accuses President Barack Obama of going back on a promise to run a transparent administration and suggests he is the true "traitor" for supposedly betraying a generation of "young, technically minded people" such as Snowden and Bradley Manning, the US Army soldier charged with aiding the enemy who is presently on trial after he gave classified material to WikiLeaks.

"The US government is spying on each and every one of us, but it is Edward Snowden who is charged with espionage for tipping us off. It is getting to the point where the mark of international distinction and service to humanity is no longer the Nobel Peace Prize, but an espionage indictment from the US Department of Justice," said Assange.

"The charging of Edward Snowden is intended to intimidate any country that might be considering standing up for his rights. That tactic must not be allowed to work. The effort to find asylum for Edward Snowden must be intensified. What brave country will stand up for him, and recognize his service to humanity? Tell your governments to step forward. Step forward and stand with Snowden."

Several American politicians have backed the decision to charge Snowden. Senator Bill Nelson, a Florida Democrat and a member of the Senate armed services committee, said in a statement on Friday: "I've always thought this was a treasonous act. Apparently so does the US Department of Justice. I hope Hong Kong's government will take him into custody and extradite him to the US."

Congressman Peter King, a Republican from New York, also praised the move. "I fully support the efforts of the United States government to indict and prosecute Edward Snowden to the fullest extent of the law," he said, according to Fox News. "He has betrayed his country and the government must demand his extradition at the earliest date."

King last week called for the prosecution of Glenn Greenwald, the Guardian journalist who has been heavily involved in breaking the NSA surveillance stories.

John Miller, a CBS News correspondent who is a former government intelligence worker, said on CBS that the extradition treaty between the US and Hong Kong has been "used a lot … that's the good news, which is this won't be a rusty process. The complicating factor is it's a complicated process."

The Government Accountability Project, a US whistleblower support group, issued a statement backing Snowden. It read: "He disclosed information about a secret program that he reasonably believed to be illegal, and his actions alone brought about the long-overdue national debate about the proper balance between privacy and civil liberties, on the one hand, and national security on the other.

"Charging Snowden with espionage is yet another effort to retaliate against those who criticize the overreach of US intelligence agencies under this administration. The charges send a clear message to potential whistleblowers: this is the treatment they can expect should they speak out about constitutional violations."