BUNGAY: Julian Assange said Friday it was “increasingly likely” the US would try to extradite him on charges related to WikiLeaks, as he spent his first day on bail on an English country estate.

The 39-year-old founder of the whistle-blowing website is fighting extradition to Sweden, where he is wanted for questioning over allegations that he sexually assaulted two women, which he denies.

But speaking outside Ellingham Hall, a friend's mansion in eastern England, where he must live while on bail, Assange said he was more concerned about potential moves from US authorities.

“The big risk, the risk we have always been concerned about, is onwards extradition to the United States. And that seems to be increasingly serious and increasingly likely,” the Australian told reporters.

Assange said his lawyers believed a secret US grand jury investigation had been started into his role in WikiLeaks' release of thousands of leaked US diplomatic cables -- a probe he condemned as “illegal”.

Looking relaxed and wearing a green puffa jacket in the snowy conditions, he said the mansion was a “big improvement” on the London jail where he was held in solitary confinement for nine days before his release on bail Thursday.

Media reports suggest that US prosecutors are trying to build a case against Assange on the grounds that he encouraged a US soldier, Bradley Manning, to steal US cables from a government computer and pass them to WikiLeaks.

Assange said: “I would say that there is a very aggressive investigation, that a lot of face has been lost by some people, and some people have careers to make by pursuing famous cases.”

He said WikiLeaks had pledged 50,000 dollars (38,000 euros) towards Manning's legal fund.

But he told ABC television in the US that: “I had never heard of the name Bradley Manning before it was published in the press.

“WikiLeaks technology (was) designed from the very beginning to make sure that we never know the identities or names of people submitting us material.”

Later, in interviews with British media, Assange said Manning “is the only one of our military sources who has been accused and that means that he is in a difficult position.”

Meanwhile, in Washington a report by congressional researchers said the Espionage Act and other US laws could be used to prosecute Assange, but there is no known precedent for prosecuting publishers in such a case.

“Leaks of classified information to the press have only rarely been punished as crimes, and we are aware of no case in which a publisher of information obtained through unauthorized disclosure by a government employee has been prosecuted for publishing it,” the report said.

On the Swedish case against him, the former computer hacker claimed it was part of a “smear campaign” linked to WikiLeaks, saying prosecutors had yet to provide “a single piece of evidence” to back up its allegations.

Swedish prosecutors deny their case is related to WikiLeaks. Assange's release was the result of a nine-day legal battle following his arrest in London on a Swedish warrant on December 7.

Although a judge in a lower court granted him bail Tuesday, prosecuting lawyers appealed. It was only after the appeal was rejected in the High Court Thursday that Assange could be freed on bail.

Judge Duncan Ouseley rejected the argument that Assange was likely to flee the country, but his supporters had to come up with a 240,000-pound (283,000-euro, 374,000-dollar) surety.

Assange has also been electronically tagged, is subject to a curfew and must report daily to a police station near the mansion in picturesque Suffolk. He was driven out of the mansion to report to police Friday.

The mansion is owned by Vaughan Smith, a former army officer and journalist who founded the Frontline Club in London which acts as WikiLeaks' British base. He has described Assange as “courageous”.

Assange has vowed the allegations against him will not stop WikiLeaks from releasing further documents.

“People like to present Wikileaks as just me and my backpack -- it is not true. We're a large organisation,” he told reporters Friday.