Reporters Without Borders (RSF) on Friday urged a UK minister not to extradite WikiLeaks founder Julian Assange to the US, in the interests of media freedom.

RSF and other media rights groups released an open letter to Home Secretary Priti Patel, whose formal approval is needed for Assange's extradition, urging her to "reject the US government's extradition request".

They said she should "act in the interest of press freedom" and immediately release Assange from prison.

A UK court on Wednesday issued a formal order to extradite Assange to face trial in the US, where he could spend a lifetime in prison for publishing secret military and diplomatic files.

The decision now rests with Patel, although Assange may still appeal within 14 days of any decision to approve the extradition.

Assange, an Australian national, is wanted to face trial for violating the US Espionage Act and could face a sentence of up to 175 years in jail if found guilty.

The campaign groups warned Patel that Assange, once in the US, would be "unable to adequately defend himself" in court as public interest is not a defence under anti-espionage legislation. 

They also said that he was likely to be detained in conditions that would "severely exacerbate his risk of suicide".

"His prosecution would set a dangerous precedent that could be applied to any media outlet that published stories based on leaked information, or indeed any journalist, publisher or source anywhere in the world," their open letter said.

Assange has been held in London's high-security Belmarsh prison since 2019 for skipping bail on the Swedish charges, which were dropped in 2020.