(CNN) - Julian Assange was too ill to appear via video link at a court hearing in London on Thursday, his lawyer said, after WikiLeaks expressed "grave concerns" about the health of its founder and said he had been moved to the medical ward of his prison.
Assange had been expected to participate in the hearing at Westminster Magistrates' Court via video link, but was instead represented solely by his solicitor, who told the chief magistrate his client was "not very well."
The hearing, on an extradition request from the United States over a computer hacking conspiracy charge, was adjourned until June 12 and could next take place in Belmarsh prison, where the publisher is being detained.
"It may be more convenient for everyone if it's there," chief magistrate Emma Arbuthnot said.
Earlier on Thursday, WikiLeaks released a statement on Assange's wellbeing. "During the seven weeks in Belmarsh his health has continued to deteriorate and he has dramatically lost weight," the statement read. "The decision of prison authorities to move him to the health ward speaks for itself."
"Mr. Assange's health had already significantly deteriorated after seven years inside the Ecuadorian embassy, under conditions that were incompatible with basic human rights," the statement added.
Assange appeared frail when he was arrested at the Ecuadorian Embassy in April, having spent seven years holed up inside the building as part of a bid to avoid being extradited to Sweden over allegations of sexual assault.
Earlier this month he appeared via video link at the initial hearing on the US extradition request, to which he insisted he would not surrender. Lawyer Ben Brandon, representing the US government, said Assange conspired with former Army intelligence analyst Chelsea Manning to obtain a "vast amount of classified documents."
The charge is just part of a mountain of legal troubles facing Assange. Last week, he was charged with 17 new counts in the US under the Espionage Act for his role in unlawfully encouraging, receiving and publishing national defense information in concert with Manning, setting up a major legal battle over First Amendment protections in the Trump era.
June 12 is the deadline for the US to submit all of its evidence on the computer hacking charge. Assange is also battling an allegation of rape in Sweden, which he has denied. Authorities there re-opened an investigation into the case earlier this month.
The Australian is currently serving a jail sentence of almost a year in London for skipping bail in 2012 when he sought political asylum in the Ecuadorian embassy.
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