LONDON - A British judge said Monday that WikiLeaks founder Julian Assange must attend his next court hearing unless he can provide medical evidence to support his absence.

Lawyers for Assange said he could not attend the latest hearing on his U.S. extradition case by video link from prison for medical reasons.

District Judge Vanessa Baraitser set another hearing date of July 27 and said Assange must appear "unless there is medical evidence" to explain his non-attendance.

The 48-year-old Australian has been indicted in the U.S. on 18 charges over the publication of classified documents. Prosecutors say he conspired with U.S. army intelligence analyst Chelsea Manning to crack a password, hack into a Pentagon computer and release secret diplomatic cables and military files on the wars in Iraq and Afghanistan.

Last week the U.S. Justice Department added a new, superseding, indictment that alleges Assange conspired with members of hacking organizations and sought to recruit hackers to provide WikiLeaks with classified information. The indictment does not add any new charges, but broadens the allegations against Assange.

Assange was arrested last year after being evicted from the Ecuadorian Embassy in London, where he had sought refuge to avoid being sent to Sweden over allegations of rape and sexual assault.

He is in London's Belmarsh Prison awaiting a full extradition hearing, which has been postponed because of the coronavirus pandemic. Originally due to begin in May, it is now scheduled to start on Sept. 7.