London (CNN) Julian Assange appeared in a London court by videolink from a high-security prison on Thursday as his battle against extradition to the United States on a computer hacking conspiracy charge got underway.

The WikiLeaks founder, speaking from Belmarsh prison, wore a sports jacket and was not handcuffed.

Asked by Judge Michael Snow if he wished to surrender himself for extradition, Assange said: "I do not wish to surrender myself for extradition for doing journalism that's won many, many awards and affected many people."

Lawyer Ben Brandon, representing the US government, said that the provisional arrest warrant for the 47-year-old was based on an indictment filed in Virginia for "one offense of attempting to access a computer without consent and accessing a computer without authorization."

"Chelsea Manning (a former US Army intelligence specialist) downloaded a vast amount of classified documents. This included four databases with nearly 90,000 Afghan war reports, 400,000 Iraq significant activity reports ... (and) 250,000 state department cables," Brandon said.

Manning then provided the documents to WikiLeaks, Brandon continued. He added that evidence collected during the course of the US investigation showed the pair "unlawfully conspired to effect these disclosures" and that Assange "agreed to help Manning crack a password that was connected to a government server."

Brandon said the maximum sentence for this type of offense is five years, adding that the full request from the US government had not yet been received.

Judge Snow said proceedings would be adjourned until May 30, when another procedural court date will take place. "The full extradition hearing is many months away where the substance of your case is likely to be argued," he added.

Outside Westminster Magistrates' Court, dozens of Assange supporters -- including around 80 "yellow vest" protesters visiting from France -- rallied, waving signs and briefly blocked a main road nearby.

A large truck with a billboard that read "#FreeSpeech" and showing Assange and Manning with American flags covering their mouths also disrupted traffic. The road was reopened after police arrived at the scene.

Supporters outside Westminster Magistrates' Court on Thursday during a hearing into the US extradition request of WikiLeaks' founder Julian Assange.

This was the second court appearance of the week for the Australian, who on Wednesday was handed a jail term of almost a year for skipping bail in 2012 when he sought political asylum in the London's Ecuadorian embassy.

Assange was wanted in Sweden for questioning over sexual assault and rape allegations. The whistleblower -- who has repeatedly denied any wrongdoing -- said he sought refuge over fears of onward rendition from Sweden to the US due to his work with WikiLeaks.

His near seven-year stint in the embassy was brought to a dramatic close on April 11 when Ecuador withdrew his asylum and invited in British police, citing Assange's bad behavior. He was then forcibly hauled out by officers.

Extradition 'where the real battle begins'

Thursday marked the start of what will likely be a long and protracted extradition fight. While Assange is presently only facing one charge, US prosecutors have signaled more charges could be on the way

UK Home Secretary Sajid Javid told Members of Parliament on April 11 that the US has up to 65 days -- or until mid-June -- to send full extradition papers.

"They have the ability to add more charges before the 15th of June but our main concern is the fact that the allegations that are being made engage protected journalistic activities," Jennifer Robinson, a lawyer for Assange, told CNN after the court adjourned on Thursday.

She continued: "The allegations boil down to, as we heard in court, not about hacking, there is no suggestion that Julian Assange had actually hacked anything. What this is actually about, is the fact that he had conversations with a source about releasing information, encouraged that source to provide more information, and talked to that source about protecting their identity."

"This is what journalists do all the time, and if he's going to be extradited and prosecuted for that activity, then that sets a great chilling impact to all journalists," she ended.

A day before, WikiLeaks' Editor-in-Chief Kristinn Hrafnsson said the US extradition claim is "where the real battle begins."

"Although the extradition is based on a lower level of offenses, we think that is basically a snaring strategy to get him to United States where additional charges will be added," Hrafnsson explained.

Mounting a defense

Extradition requests to the UK from outside the European Union are governed by Part 2 of the Extradition Act 2003. When reviewing the US extradition claim, it will not be for the UK courts to determine culpability. A judge only determines whether the US request satisfies the "dual criminality" legal requirement -- meaning that the alleged crime is illegal in both countries. The judge would also consider if granting extradition would breach Assange's human rights.

If satisfied that the claim meets procedural conditions, the case would be sent to the British home secretary for a final decision on ordering the extradition.

On Wednesday, Robinson told CNN they wanted to wait to review the full extradition request before revealing their defense strategy.

"We need to wait to see the final extradition request from the United States to determine what our arguments will be," Robinson said outside Southwark Crown Court.

Assange's lawyers are likely to argue that the extradition request is politically motivated and that he would not be able to receive a fair trial in the US, according to Nick Vamos, the former head of extradition at the Crown Prosecution Service where he was responsible for the case.

"It's going to be one of those where he throws the kitchen sink at it, I think that's clear," Vamos told CNN.

Vamos added that "a whiff of political motivation" would not be enough to prevent extradition.

"What you need to prove is that the entire proceedings are corrupted and tainted by politics and that the person who is being prosecuted solely or primarily on the basis of their political beliefs, their political opinions, or political activities," he explained.