The anti-secrecy international organisation was founded in 2006 by Australian Julian Assange. The non-profit group calls itself a media organisation and also acts as an online "drop box" for anonymous sources to leak information and documents to journalists. In 2010, WikiLeaks became more prominent after releasing the "Collateral Murder" video, which showed US Army helicopter firing on a group of mostly unarmed men, two of whom were journalists.
WikiLeaks founder Assange likely to avoid secrecy charges in US
Justice Department cannot indict WikiLeaks founder for publishing classified documents without also prosecuting news organisations
The US Justice Department has "all but concluded" it will not bring charges against WikiLeaks founder Julian Assange for publishing classified documents.
Government lawyers said they could not do so without also prosecuting US news organisations and journalists.
Officials stressed that a formal decision had not been taken, and a grand jury investigating WikiLeaks remained impanelled.
But they said there was little possibility of bringing a case against Assange, unless he is implicated in criminal activity other than releasing online top secret military and diplomatic documents.
The Obama administration has charged government employees and contractors who leak classified information - such as former National Security Agency contractor Edward Snowden and former army intelligence analyst Bradley Manning - with violations of the Espionage Act.
But officials said that although Assange published classified documents, he did not leak them, something they said significantly affected their legal analysis.
"The problem the department has always had in investigating Assange is there is no way to prosecute him for publishing information without the same theory being applied to journalists," said ex-Justice Department spokesman Matthew Miller.
"And if you are not going to prosecute journalists for publishing classified information, which the department is not, then there is no way to prosecute Assange."
The officials said that if the Justice Department indicted Assange, it would also have to prosecute The New York Times and other news organisations and writers who published classified material, including The Washington Post and Britain's The Guardian.
WikiLeaks spokesman Kristinn Hrafnsson said last week that the anti-secrecy organisation is sceptical "short of an open, official, formal confirmation that the US government is not going to prosecute WikiLeaks". Justice Department officials said it was unclear whether there would be a formal announcement should the grand jury investigation be formally closed.
Barry Pollack, a Washington-based attorney for Assange, said: "We have repeatedly asked the Department of Justice to tell us what the status of the investigation was with respect to Mr Assange. They have declined to do so.
"They have not informed us in any way that they are closing the investigation or have made a decision not to bring charges against Mr Assange.
"While we would certainly welcome that development, it should not have taken the Department of Justice several years to come to the conclusion that it should not be investigating journalists for publishing truthful information."
In an interview with The Washington Post earlier this month, Attorney General Eric Holder said Justice Department officials were still trying to repatriate Snowden, who has obtained temporary asylum in Russia, to stand trial.
But Holder said the Justice Department was not planning to prosecute former Guardian reporter Glenn Greenwald, one of the journalists who received documents from Snowden.
Assange has been living in a room in the Ecuadorean embassy in London since Ecuador granted him political asylum.
He is facing charges of sex assault in Sweden.
Assange and his supporters have said the Australian national fears that if he goes to Sweden to face those charges, he will be extradited to the US.