Wikileaks founder Julian Assange attended court in London on Wednesday, as lawyers from the U.S. government launched a new attempt to have him extradited.
Assange, who is Australian, remains wanted in the United States on 18 criminal charges over the massive document dumps WikiLeaks published in 2010, containing thousands of secret U.S. government and military files, and diplomatic communications.
It included documents from the wars in Iraq and Afghanistan, that U.S. prosecutors allege put lives at risk.
The U.S. is appealing an earlier ruling by a London judge that Assange should not be extradited because he would likely commit suicide in a U.S. prison.
Assange supporters gathered outside the hearing.
"It is unconscionable, unprecedented. Have you ever heard of a country allowing the extradition of one of its protected political asylees to the very country that wants to murder him? This is insane, this is wrong, this is completely outside any legal process."
A U.S. lawyer told the court that Washington had addressed the suicide concerns by making assurances over how Assange would be treated if extradited. These included that he would not be detained at a maximum security prison Colorado, known as ADX.
The U.S. authorities had also assured Britain that they would consent to Assange serving in Australia any custodial sentence imposed by a U.S. court.
Assange, who denies any wrongdoing, is currently being held at the UK's Belmarsh Prison.
WikiLeaks first rose to prominence in 2010 when it published a secret U.S. military video showing an Apache helicopter killing a dozen people in Iraq, including two Reuters journalists.
It also played major role in the 2016 election with the release of hacked emails related to Hillary Clinton's presidential campaign.