London — More than 60 doctors have written to British authorities asserting that WikiLeaks founder Julian Assange urgently needs medical treatment at a university hospital. The doctors said in a letter published Monday that Assange suffers from psychological problems including depression as well as dental issues and a serious shoulder ailment.

Assange is in Belmarsh Prison on the outskirts of London in advance of an extradition hearing set for February. He is sought by the U.S. on espionage charges relating to his WikiLeaks work.

The letter, distributed by WikiLeaks, was sent to Home Secretary Priti Patel, who heads up the British government agency in charge of law enforcement. It was also addressed to Patel's political counterpart from the opposition party, Shadow Home Secretary Diane Abbot.

Dr. Lissa Johnson of Australia, Assange's home country, said an independent medical assessment was needed to determine if Assange is "medically fit" to face legal proceedings.

In the letter, Johnson and the other doctors from a range of different countries warn that, in their opinion, if Assange does not receive the medical attention they say he requires, "we have real concerns, on the evidence currently available, that Mr Assange could die in prison. The medical situation is thereby urgent. There is no time to lose."

Last week Sweden dropped its investigation into an alleged rape by Assange because too much time has elapsed since the accusation was made over nine years ago. Assange has always denied the allegations made against him during a visit to Stockholm in August 2010.

"Nine years have gone," Swedish prosecutor Eve-Marie Persson said. "Time is a player in this. The oral evidence has weakened as time has passed."

Two months earlier, Assange was evicted from the Ecuadorean Embassy in London where he had been holed up for nearly seven years. He was immediately arrested and is currently serving a 50-week sentence in Britain for jumping bail in 2012.

Kristinn Hrafnsson, WikiLeaks editor-in-chief, said in a tweet that the focus should now move to the "threat" that Assange has been "warning about for years: the belligerent prosecution of the United States and the threat it poses to the First Amendment."

The Australian faces an 18-count indictment in the Eastern District of Virginia that accuses him of soliciting and publishing classified information and with conspiring with former Army intelligence analyst Chelsea Manning to crack a Defense Department computer password.