Assange, who has been holed up in Ecuador's embassy in London since seeking asylum in 2012, is considered a wanted man by United States law enforcement agencies after his controversial publication of classified diplomatic cables and other secret U.S. government documents.
Any arrest could have an impact on the investigation in the USA into any ties between Russian Federation and the 2016 presidential campaign.
Assange and his supporters have periodically said USA authorities had filed secret criminal charges against him, an assertion against which some U.S. officials pushed back until recently.
The disclosure (see below), made in August by Assistant US Attorney Kellen S. Dwyer, urges the Eastern District Court of Virginia to keep the matter sealed, writing that "due to the sophistication of the defendant and the publicity surrounding the case, no other procedure is likely to keep confidential the fact that Assange has been charged". Prosecutors are known to copy text from past court filings to make similar arguments in new cases, typically changing names and other relevant details accordingly.
Barry Pollack, one of Assange's attorneys, said, "The only thing more irresponsible than charging a person for publishing truthful information would be to put in a public filing information that clearly was not intended for the public and without any notice to Mr. Assange".
"The news that criminal charges have apparently been filed against Mr. Assange is even more troubling than the haphazard manner in which that information has been revealed", Pollack said in an email.
The Wall Street Journal reported earlier on Thursday that Justice Department officials were preparing to prosecute Assange. Officials have alleged the emails were hacked by Russian spies and transferred to WikiLeaks.
It also said that the charges would "need to remain sealed unto Assange is arrested". Seitu Sulayman Kokayi, 29, was charged with enticing a 15-year-old girl to have sex with him and send him pornographic images of herself.
Throughout that time, the United States has refused to say whether there are any sealed charges against Assange.
Wikileaks tweeted the revelation was an "apparent cut-and-paste error".
Assange, who had leaked tons of classified documents in 2010, has been living in hiding in Ecuador.
The DOJ is increasingly optimistic about the prospect of bringing Julian Assange before a USA court and is reportedly planning to formally charge the whistleblower in the hope of getting him out of the Ecuadorean embassy in London.