Julian Assange has been ordered to face a full extradition hearing in the UK next year.
The WikiLeaks founder is fighting against being sent to the US to face 18 charges that relate to the leaking of government secrets.
Allegations include conspiring to hack into a classified Pentagon computer.
The US extradition case was formally opened at Westminster Magistrates' Court today, a day after an extradition request was signed off by home secretary Sajid Javid.
Appearing via video-link from Belmarsh Prison, Assange told the court that years of his life was "effectively at stake", as he sought to defend his organisation.
He argued that WikiLeaks was "nothing but a publisher".
Mark Summers QC, representing Assange, said there was a "multiplicity of profound issues" with the extradition case.
"We say it represents an outrageous and full-frontal assault on journalistic rights," he said.
But Ben Brandon, who was representing the US, said the case was linked to "one of the largest compromises of confidential information in the history of the United States".
Chief magistrate Emma Arbuthnot has ordered for a full extradition hearing expected to last five days to begin on February 25, 2020.
Assange is currently serving a 50-week prison term for a bail breach. He is set to appeal against the sentence.