American federal prosecutors have been pressing witnesses in the U.S. and abroad to testify against WikiLeaks founder Julian Assange, WikiLeaks says, offering further evidence that the Justice Department is building a criminal case against the man who leaked Democratic emails hacked by the Russians in the 2016 election.

In a new submission to the Inter-American Commission of Human Rights, based in Washington, WikiLeaks is urging the Justice Department to unseal the charges that appear to have been secretly filed against Assange in the Eastern District of Virginia. A mistake in a Justice Department court filing in November inadvertently suggested the existence of those charges.

"The submission reveals for the first time that U.S. federal prosecutors have in the last few months formally approached people in the United States, Germany and Iceland and pressed them to testify against Mr. Assange in return for immunity from prosecution," WikiLeaks said in a statement. "Those approached are associated with WikiLeaks' joint publications with other media about U.S. diplomacy, Guantanamo Bay and the wars in Iraq and Afghanistan."

The statement also suggests that the U.S. has been working with Ecuador to monitor Assange in his residence in exile at the Ecuadorian embassy in London, an assertion that former intelligence officials say is plausible. In 2017, then-CIA director Mike Pompeo declared WikiLeaks a "hostile intelligence service."

A Justice Department spokesperson declined to comment, and an American lawyer for Assange referred NBC News to a lawyer in London, who did not immediately respond to a request for comment.

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The statement makes no mention of WikiLeaks' role in leaking Democratic emails that had been hacked by Russian intelligence officers as part of an effort to help Donald Trump win the 2016 presidential election.

Special counsel Robert Mueller is investigating the role played by WikiLeaks in that matter, court documents show, though the investigation in Virginia goes back to 2010, well before the Russian election interference campaign.

A lawyer for Reporters Committee for Freedom of the Press, which is fighting to have the Virginia case unsealed, said the secrecy around the case deprives the public of knowing whether it presents any First Amendment concerns.

"Whether the charges against Mr. Assange are made public by the district court in response to the Reporters Committee's motion, or whether they are made public as a result of separate actions being taken by Mr. Assange on his own behalf, we think the public will benefit from knowing what those charges are," said Katie Townsend, the group's legal director.

The WikiLeaks statement seeks to portray the anti-secrecy group as a journalistic organization, and raises the specter that the Trump administration is seeking to prosecute journalists for reporting on classified information.

"The Trump Administration … is clearly intent on using the prosecution of Julian Assange as an 'icebreaker' to set a dangerous precedent that would enable the prosecution of most serious media organizations, such as The New York Times, the Washington Post, AP, CNN and NBC which routinely obtain and publish information from classified sources," the statement says.

But many legal experts believe any prosecution of Assange would have to be predicated on evidence that he induced people to break the law by providing WikiLeaks with classified information. There are also longtime suspicions that WikiLeaks has been working closely with Russian intelligence.

The New York Times reported in 2016 that WikiLeaks disclosures often have benefited Russia at the expense of the West, and that WikiLeaks has not made any major disclosures that have spotlighted Russia's foibles.

The WikiLeaks twitter account, widely believed to be controlled by Assange, corresponded in 2016 with Donald Trump Jr., according to messages that have become public.

On Oct. 3, 2016, WikiLeaks wrote to Trump Jr.: "Hiya, it'd be great if you guys could comment on/push this story," attaching a quote from then-Democratic nominee Hillary Clinton about wanting to "just drone" Assange, according to messages made public by The Atlantic.

"Already did that earlier today," Trump Jr. responded an hour-and-a-half later. "It's amazing what she can get away with."

Trump Jr.'s lawyer said he did nothing wrong.