The legal team for Julian Assange is moving quickly to appeal the decision by UK Home Secretary Priti Patel to approve the extradition of the WikiLeaks founder to the United States.
The US has filed 18 criminal charges against Mr Assange, including espionage and hacking, connected to the publication in 2010 of US military documents related to the Afghanistan conflict.
If convicted, lawyers for the Australian-born founder of Wikileaks have said he could face a jail term of 175 years. US lawyers said they believe the jail term would be more like four to six years.
A spokesperson for the UK Home Office said a range of factors were considered by Ms Patel.
"In this case, 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."
Ms Patel has been weighing the decision since last month after the provided by US authorities on how Mr Assange is likely to be treated.
Julian Assange's team moves to file appeal
Ms Patel's decision does not mean the end of Mr Assange's legal battle, which has been going on for more than a decade.
The Home Office said while the extradition request had been approved, Mr Assange still has 14 days to appeal the decision.
Legal advisor to Australian Assange Campaign, Greg Barns SC, said there will be an appeal to try to overturn the ruling.
"This matter will go back into the courts but it's an opportunity again to remind Australians of the need to ensure this Australian citizen doesn't face 170 years for revealing war crimes committed by the US," he told SBS News.
"We've been strongly supportive of the recent comments by Prime Minister [Anthony] Albanese and Foreign Minister [Penny] Wong about the need for early resolution of this case and again we would urge them to get involved, particularly at this point in time, to ensure Julian Assange can walk out of Belmarsh Prison."
Mr Assange can seek to appeal through London's High Court, and ultimately he can take his case to the UK Supreme Court.
But if an appeal is refused, Mr Assange must be extradited within 28 days.
'A dark day for press freedom'
Wikileaks condemned Ms Patel's decision, saying it is a "dark day for press freedom and British democracy".
"Anyone in this country who cares about freedom of expression should be deeply ashamed that the Home Secretary has approved the extradition of Julian Assange to the United States, the country that plotted his assassination," the organisation said in a statement.
"Make no mistake, this has always been a political case. Julian published evidence that the country trying to extradite him committed war crimes and covered them up... Their revenge is to try to disappear him into the darkest recesses of their prison system for the rest of his life to deter others from holding governments to account."
Independent MP Andrew Wilkie urged Australian Prime Minister Anthony Albanese to pick up the phone and "demand an end to this madness".
"The decision by the UK Govt to approve extradition of Julian Assange to the US is an outrageous betrayal of rule of law, media freedom and human rights," he said in a statement posted on Twitter.
Foreign Minister Penny Wong said the Department of Foreign Affairs and Trade will provide consular assistance and that Australian officials will convey to US and UK authorities the need for Mr Assange to have "due process, human and fair treatment".
"The Australian Government has been clear in our view that Mr Assange’s case has dragged on for too long and that it should be brought to a close," she said in a joint statement with Attorney-General Mark Dreyfus.
"We will continue to convey our expectations that Mr Assange is entitled to due process, humane and fair treatment, access to proper medical care, and access to his legal team."
The 50-year-old has been held in Belmarsh prison in London for the last three years as he fights the extradition request from the US. Prior to that he spent seven years in the Ecuadorean embassy in London.
Sweden in 2010 launched a case seeking Mr Assange's extradition on allegations of sex crimes, but has since dropped the legal action.
