Assange, 47, appeared at Westminster Magistrates Court in London after being accused by US authorities of conspiring to hack computers and of violating espionage law.
The court ruled that a full extradition hearing, which is expected to last five days, will begin on 25 February. A hearing will be held before that in October.
Assange, who appeared with a scraggly white beard, is being held in Belmarsh prison in London, after being jailed for 50 weeks for skipping bail.
In April, he was evicted from Ecuador’s embassy in London, where he had been holed up since 2012 after the country granted him political asylum. He had been avoiding extradition to Sweden for questioning over alleged sexual assault.
He told the court on Friday: “175 years of my life is effectively at stake.” The WikiLeaks founder also spoke to defend his website against hacking claims, by saying it ”is nothing but a publisher”.
Outside the court, his legal team branded charges in the US “an outrageous and full-frontal assault” on journalistic rights.
Earlier this week, justice officials in Washington formally submitted an extradition request to the UK over claims Mr Assange published classified information and conspired with former US army soldier Chelsea Manning to crack a defence department computer password.
A request to extradite Mr Assange to the US has been signed by Sajid Javid, the home secretary, but must still be approved by the courts. Speaking on the Today programme, Mr Javid said: “I am very pleased that the police were finally able to apprehend him and now he is rightly behind bars because he broke UK law.”
Mr Assange does not have access to a computer in prison and has been moved to the medical wing after his health allegedly deteriorated. At a previous hearing in May, he was too ill to appear via video link.
Supporters of Mr Assange protested outside the court, waving banners and chanting “no extradition”.