The brother and wife of the WikiLeaks founder said Friday they will explore all avenues to block the UK ruling.
Family members of Julian Assange have promised to fight the UK's decision to extradite him to the United States (US).
On Friday, the UK government ordered the extradition of WikiLeaks founder to the US to face spying charges. He has 14 days to appeal.
"If he's extradited to the United States the conditions he [Assange] will be under will be so oppressive," said Gabriel Shipton, Assange's brother, at a press conference on Friday. "It will drive him to take his own life."
The Home Office said in a statement that “the UK courts have not found that it would be oppressive, unjust or an abuse of process to extradite Mr Assange.”
“Nor have they found that extradition would be incompatible with his human rights, including his right to a fair trial and to freedom of expression, and that whilst in the US he will be treated appropriately, including in relation to his health.”
UK Home Secretary Priti Patel signed the extradition order on Friday, following a British court ruling in April that Assange could be sent to the US.
At the press conference outside the British Consulate in New York, Shipton claimed the announcement had far-reaching implications for reporters and the freedom of speech.
"What this decision means is that basic journalism, journalism that people do every day, sourcing information, publishing information, is now illegal in the UK," he alleged.
Following the publication of thousands of confidential papers and diplomatic cables by Wikileaks in 2010, Assange was charged in the US with 18 criminal counts.
Lawmakers have claimed the release of this sensitive material endangered military personnel on active duty and undermined US security.
The decision is a big moment in Assange’s years-long battle to avoid facing trial in the US, though not necessarily the end of the tale if he appeals the latest decision.
His wife Stella Moris said Saturday they were exploring possible avenues to block the UK's ruling.
A British judge first approved the extradition in April, leaving the final decision to the government. Friday's ruling came after a legal battle that went all the way to the UK Supreme Court.
The US has asked British authorities to extradite Assange so he can stand trial on 17 charges of espionage and one charge of computer misuse over WikiLeaks’ publication of a huge trove of classified documents more than a decade ago.
American prosecutors say Assange unlawfully helped US Army intelligence analyst Chelsea Manning steal classified diplomatic cables and military files that WikiLeaks later published, putting lives at risk.
Journalism organisations and human rights groups have called on Britain to refuse the extradition request.
Supporters and lawyers for Assange, 50, argue that he was acting as a journalist and is entitled to First Amendment protections of freedom of speech for publishing documents that exposed US military wrongdoing in Iraq and Afghanistan.
They argue that his case is politically motivated.
Assange’s lawyers say he could face up to 175 years in jail if he is convicted in the US, though American authorities have said any sentence is likely to be much lower than that.
Wikileaks said Friday Assange would appeal his extradition from Britain to the United States.
“Today is not the end of the fight. It is only the beginning of a new legal battle. We will appeal through the legal system,” a statement posted on the Wikileaks Twitter accounts said.
Assange has been held at Britain’s high-security Belmarsh Prison in London since 2019, when he was arrested for skipping bail during a separate legal battle. Before that, he spent seven years inside the Ecuadorian Embassy in London to avoid extradition to Sweden to face allegations of rape and sexual assault.
Sweden dropped the sex crimes investigations in November 2019 because so much time had elapsed.