A U.N. expert said Julian Assange has experienced nine years of "severe abuse" and noticed signs of "constant anxiety" coming from the Wikileaks founder | Jack Taylor/Getty Images Julian Assange has suffered psychological abuse, says UN expert ‘What was worrying was the psychological side and his constant anxiety.’

A U.N. expert said Julian Assange has experienced nine years of "severe abuse" and will urge the U.K. government to abandon plans to extradite the WikiLeaks founder to the U.S.

Nils Melzer, the U.N.'s special rapporteur on torture and a former legal adviser to the Red Cross, is expected to send a letter to the British government Friday on behalf of the 47-year-old Australian, who is accused of violating the U.S. Espionage Act and could be sentenced to decades in prison, the Guardian reported.

"What was worrying was the psychological side and his constant anxiety," Melzer said following a meeting with Assange in prison earlier this month, during which he was also examined by medical experts. "It was perceptible that he had a sense of being under threat from everyone ... It was difficult to have a very structured conversation with him."

Assange, who in 2012 sought political asylum in the Ecuadorian Embassy in London in order to avoid extradition to Sweden following sexual assault allegations, was taken into police custody in April following the revocation of his asylum status. He was subsequently given a 50-week prison sentence for violating the conditions of his bail.

"In the course of the past nine years, Mr Assange has been exposed to persistent, progressively severe abuse ranging from systematic judicial persecution and arbitrary confinement to the Ecuadorian embassy, to his oppressive isolation harassment and surveillance inside the embassy, and from deliberate collective ridicule, insults and humiliation," Melzer is expected to say. Assange voluntarily moved into the embassy.

According to a spokesperson for the British government, the U.K. has a "close relationship" with U.N. bodies, and remains "committed to upholding the rule of law," the Guardian reported.

"We support the important work of the special rapporteur's mandate and will respond to his letter in due course, but we disagree with a number of his observations."