LONDON - WikiLeaks founder Julian Assange was released from a British jail cell Thursday after the High Court upheld a decision granting him bail. Assange retreated to a friend's country estate, where he planned to help mount his legal defense against extradition to Sweden to face sex-crime allegations.

Triumphantly raising his arm as he walked out of the central London courthouse, Assange declared: "If justice is not always an outcome, at least it is not dead yet."

Describing his nine nights in jail as "solitary confinement in the bottom of a Victorian prison," he thanked his attorneys and supporters, including the prominent backers who posted his bail, before vowing to continue WikiLeaks' work as he tries to prove what he described as his innocence in the sex-crime cases.

The High Court's ruling amounts to the beginning of Assange's legal troubles. He must now prepare for a full extradition trial in February.

At the same time, U.S. law enforcement and other sources say that federal prosecutors are seeking evidence that Assange, whose WikiLeaks Web site released thousands of classified U.S. government cables on the Internet, conspired with a U.S. Army private to obtain the classified information from military networks.

Investigators in that case are exploring whether Assange or anyone connected to WikiLeaks helped provide Pfc. Bradley E. Manning with software that he allegedly installed without authorization on a classified military computer network, said sources familiar with the investigation. The software may have been used to help Manning in the alleged mishandling of classified data.

If Assange is somehow linked to the provision of that software, legal experts said, prosecutors may be closer to making a case for conspiracy.

"I can say they would like it very much if they could build a case around conspiracy," said Adrian Lamo, a former computer hacker who reported Manning to authorities and has been speaking with investigators.

Law enforcement sources said the possible conspiracy charge was only one avenue of inquiry in a broad investigation.

It is unclear whether charges will be brought. Mark Stephens, a British attorney for Assange, said the Justice Department told him that, contrary to previous reports, no grand jury had been empaneled.

Jennifer Robinson, another attorney for Assange, said there is "no evidence, absolutely not" of any illicit collusion between Assange and Manning.

After his release, Assange was driven off in an armored vehicle by Vaughan Smith, a London restaurateur and former war correspondent who will host Assange at his 600-acre Ellingham Hall estate northeast of London under what the British media have dubbed "mansion arrest." Before heading to the country, Assange stopped in central London for a celebratory martini with friends and well-wishers.