The US government wants Assange to face espionage charges that could put him in jail for up to 175 years, although its legal team claims his possible sentence is difficult to estimate and could be far shorter.
It has provided written pledges that Assange would not be detained at the ADX Florence jail in Colorado, which houses criminals including Al-Qaeda extremists in near-total isolation.
The US is appealing against UK district court judge Vanessa Baraitser’s decision in January that it would be “oppressive” to extradite Assange because of his serious risk of suicide and mental health deterioration in the US penal system.
She rejected US experts’ testimony that Assange would be protected from self-harm, noting that others such as disgraced US financier Jeffrey Epstein had killed themselves in custody.
“These findings arose primarily from the nature of Mr Assange’s mental disorder and his fears of extradition given the wholly exceptional nature of his case,” his lawyer Edward Fitzgerald told two senior judges reviewing the ruling.
“There is nothing to suggest that these factors have changed in the least bit with these assurances,” he added.
“That’s why we say that irrespective of the assurances, you simply can’t say she (Baraitser) would have reached a different conclusion.”