Assange was evicted last month from the Ecuadorian Embassy where he had been holed up with political asylum since 2012.
Prosecutor Eva-Marie Persson told a news conference she would continue and conclude a preliminary investigation that was dropped in 2017 without charges being brought as Assange had taken refuge in the Ecuadorean embassy in London.
If Sweden relaunches the case, that could leave Britain deciding whether to extradite him to the Scandinavian country or the United States.
The 47-year-old Australian was sentenced on May 1 to 50 weeks in prison for jumping bail in 2012 and holing up in the Ecuadorian Embassy in London.
Asked at a hearing at Westminster Magistrates' Court whether he agreed to be extradited to the United States, Assange, appearing via a video link from a British prison, said he did not wish to surrender to extradition.
Assange broke bail to enter the Ecuadorean embassy almost seven years ago.
Assange was arrested last month after Ecuador revoked his political asylum.
Trump administration officials seemed to make clear early on that they held a different view, dialling up the rhetoric on the anti-secrecy organization shortly after it made damaging disclosures about the CIA's cyberespionage tools.
WikiLeaks' first release in December 2006 was an apparent assassination order by a Somali rebel leader that may or may not have been authentic.
Read on to know how the founder of one of the world’s most controversial whistleblower hosting platforms landed himself in this soup.
Assange lived in a small apartment in the embassy where he sought refuge while facing investigation for sexual assault and rape in Sweden, claims which were later dropped.
Assange has been holed up in the Embassy of Ecuador in London since August 2012.
It was not immediately clear what prompted the advice to media organisations, but WikiLeaks singled out Britain's Guardian newspaper for publishing what it said was a false report about Assange.
Britain says Assange will be arrested for skipping bail if he leaves the embassy, but that any sentence would not exceed six months, if convicted.
Prosecutors revealed the existence of the sealed indictment inadvertently in a court filing in an unrelated case, WikiLeaks said.
Assange spoke from the embassy via teleconference at the first hearing in Quito of his lawsuit challenging the Ecuadorean government requiring him to pay for medical bills, phone calls and clean up after his pet cat.
Foreign Minister Jose Valencia said in an interview with Reuters that Ecuador's only responsibility was looking after Assange's wellbeing, after the Australian national sued the country over new conditions placed on his asylum in the London embassy.
Assange sought refuge at the Ecuador Embassy in Knightsbridge in June 2012, having lost an appeal against extradition to Sweden for questioning on allegations of rape and sexual assault that went to the Supreme Court.
The move comes nearly six months after the Ecuadorean government suspended Assange's communications in March, after he discussed issues on social media that could damage the country's diplomatic relations, including a diplomatic crisis between London and Moscow as well as Catalonian separatism.
The anti-secrecy group's chief has been based at the Ecuador embassy in central London since 2012 after he lost appeals against sexual assault charges in Sweden.
Donald Trump, Jr revealed what he said was the "entire" chain of Twitter direct messages with WikiLeaks between September 2016 and July this year, in which the anti-secrecy group sought to feed information to the Trump campaign and enhance the impact of its Clinton releases.
The former secretary of state's devastating election loss to Trump remains raw and she again lashed out at WikiLeaks founder Julian Assange and his alleged role in damaging her candidacy.
Julian Assange feels the engineer, who had sent out a diversity memo, had the right to express his opinion.
Twitter posts during the final two months of the 2016 election race shows Clinton was much more heavily criticised on social media compared with her rival Donald Trump.
Swedish prosecutors said on Friday they had dropped an investigation of WikiLeaks founder Julian Assange over a rape allegation.