LONDON — Lawyers for Julian Assange, the founder of theWikiLeaks antisecrecy group, said on Tuesday that they would oppose his extradition to Sweden because he might subsequently face “illegal rendition” to the United States, risking imprisonment at Guantánamo Bay, Cuba, or even the death penalty.
They made the assertion in defense documents released after Mr. Assange made a brief appearance in a British high-security court for a largely procedural hearing concerning his resistance to demands for his extradition to Sweden, where he has been accused of sexual misconduct.
The documents for the first time publicly named the two WikiLeaks volunteers who have accused Mr. Assange of forcing them to have sex with him without a condom in Sweden last August, in one case while the woman was asleep. In keeping with Sweden’s policy of anonymity for those involved in such cases, they had been referred to only as Ms. A and Ms. W.
Karin Rosander, a spokeswoman for the Swedish prosecutors’ office, could not immediately say whether the disclosure of the women’s names was a crime, but she said that possibility would be investigated. Jennifer Robinson, one of Mr. Assange’s London lawyers, said that the inclusion of the women’s names in the defense documents was an oversight that would be corrected.
The court scheduled the extradition hearing for Feb. 7-8. The sexual accusations, which Mr. Assange denies, have overlapped with the WikiLeaks publication of about 2,000 State Department documents — from a trove of about 250,000 in its possession — exposing confidential or secret communications to broad scrutiny on its Web site and in publications including The New York Times, The Guardian in Britain, Der Spiegel in Germany, Le Monde in France and El País in Spain.
“Our work with WikiLeaks continues unabated, and we are stepping up our publishing for matters relating to Cablegate and other materials,” Mr. Assange said after the 10-minute hearing, using his group’s term for the State Department documents. “Those will shortly be appearing through our newspaper partners throughout the world,” he said, without elaborating on the content. In recent weeks, the flow of documents has slowed to a trickle.
Mr. Assange was jailed in Britain in early December after a Swedish prosecutor issued a European arrest warrant seeking his extradition to be questioned about the sexual accusations. He was released on $370,000 bail nine days later, on Dec. 16.
In a 35-page outline of their case against extradition, released on the WikiLeaks Web site, Mr. Assange’s lawyers said, “It is submitted that there is a real risk that, if extradited to Sweden, the United States will seek his extradition and/or illegal rendition to the U.S.A., where there will be a real risk of him being detained at Guantánamo Bay or elsewhere.”
The document also cited statements by calling for the execution of those who leaked the State Department documents.
“Indeed, if Mr. Assange were rendered to the U.S.A. without assurances that the death penalty would not be carried out, there is a real risk that he could be made subject to the death penalty,” the lawyers said.
Mr. Assange’s lawyers released their outline within minutes of the court hearing. They said they would also argue that Swedish law did not permit their client to be extradited on “the mere suspicion” that he had committed a crime. The lawyers argued that Swedish prosecutors had said publicly that they were seeking his extradition solely to question him about the sexual misconduct accusations.
The defense said Mr. Assange had been “the victim of a pattern of illegal or corrupt behavior” by Swedish prosecutors, whom they accused of making a series of procedural and other errors in their handling of the case.
Previous hearings have been held in central London courts. But the one on Tuesday was set for the Belmarsh high-security court in the southeast of the city, which often handles terrorism cases. Britain’s court service said the move was intended to accommodate reporters and camera crews who had scrimmaged for position at the other courts.
Wearing a gray duffle coat over a dark suit and tie, Mr. Assange arrived with his British lawyer, Mark Stephens. Once in court, he gave a thumbs-up to associates in the public gallery.
The WikiLeaks disclosures have angered officials in Washington, and Justice Department officials are seeking to determine whether they can bring charges against him.
Prosecutors have gone to court to demand Twitter account records of several people linked to WikiLeaks, including Mr. Assange, according to the group and a copy of a subpoena made public on Friday.
The subpoena is the first public evidence of a criminal investigation, announced last month by Attorney General Eric H. Holder Jr., that has been urged by members of Congress from both parties but is fraught with legal and political difficulties for the Obama administration.
It was denounced by WikiLeaks, which has so far made public only about 1 percent of the quarter-million diplomatic cables in its possession. It has threatened to post them all on the Web if criminal charges are brought.
When Mr. Assange, a 39-year-old Australian, was released from jail last month, his bail conditions required him to stay in Ellingham Hall, a luxurious house on a 650-acre estate in eastern England; wear an electronic tag; and report to local police officers every day. He has described the conditions as “high-tech house arrest.”
He recently said he had signed deals to publish an autobiography that, he told a British newspaper, might be worth $1.7 million.
On Tuesday, the court agreed to allow him to move to central London for two days during the full extradition hearing next month. He will be staying at the Frontline Club, founded by Vaughan Smith, the owner of Ellingham Hall.
Ravi Somaiya reported from London, and Alan Cowell from Paris.