Javid said he said he signed the papers on Wednesday, a day after the U.S. Justice Department asked the United Kingdom to extradite Assange.
"First of all, I am very pleased the police were able to apprehend him and now he is rightly behind bars because he broke UK law," Javid told BBC Radio 4 on Thursday. "There is an extradition request from the U.S. that is before the courts tomorrow but yesterday I signed the extradition order and certified it and that will be going in front of the courts tomorrow.”
The UK Home Office said in a statement: "Mr Assange was arrested in relation to a provisional extradition request from the United States of America. He is accused of offences including computer misuse and the unauthorized disclosure of national defence information."
"We have received the full extradition request, which has been certified by the Home Secretary,” the statement continued, adding “This case is now before the courts and it would be inappropriate to comment further."
The U.S. will detail all of the charges against Assange on Friday when they seek his extradition in a U.K court.
U.S prosecutors initially charged Assange with a single count of computer intrusion, but last month added 17 new counts, including controversial charges under the Espionage Act for encouraging, receiving and publishing national defense information in concert with former Army intelligence analyst Chelsea Manning.
Such a charge under the Espionage Act has never been successfully prosecuted, according to CNN legal analyst Steve Vladeck.
Assange's initial indictment sparked a debate over the First Amendment and whether his alleged role in procuring secret US material constituted protected journalistic activity.
Assange lived inside the Ecuadorian embassy in London for seven years until April when the country revoked his protection and he was arrested.