London's High Court upheld bail for WikiLeaks founder Julian Assange Thursday after rejecting an appeal to keep him in jail while he fights extradition to Sweden to answer allegations of sex crimes.

Assange was in court to hear the judge reject an appeal on behalf of Swedish prosecutors against a ruling Tuesday that he be granted bail.

He endorsed the stringent bail conditions imposed by the lower court, which stated that Assange's supporters must pay a 240,000-pound ($374,000) surety and that he be subject to electronic tagging and a curfew.

Assange's lawyer, Mark Stephens, earlier indicated that the money was ready.

Meanwhile, US Federal prosecutors are looking for any evidence that Assange conspired with a former US Army intelligence analyst suspected of leaking classified government documents, The New York Times reported Wednesday.

US Justice Department officials were trying to determine whether Assange encouraged or helped Private Bradley Manning extract classified military and state department files from a government computer system, the newspaper said.

If he did, officials believe Assange could be charged as a conspirator in the leak, not just as a passive recipient and publisher of the documents, the newspaper said.

A spokesman of the Justice Department declined to comment on the report.

The Department has been looking into a range of criminal charges, including violations of the 1917 Espionage Act, which could be used to prosecute in the WikiLeaks case.

Prosecutors were studying an online chat log in which Manning is said to claim he had been directly communicating with Assange while downloading government files, The New York Times reported.

Assange has been held in a London jail after being arrested in connection with an investigation by Swedish authorities into alleged sex crimes.

Some legal experts have said it would be difficult for the Obama administration to prosecute WikiLeaks or Assange, who is an Australian citizen, for espionage. Other parts of US law, however, make it easier to prosecute foreign nationals for unauthorized disclosure of certain classified information.