"First of all, I am very pleased with the police being able to arrest him and now he is right behind the bars because he broke British law," said Javid BBC Radio 4 on Thursday.
"There is a extradition request from the United States that is before the courts tomorrow but yesterday I wrote the extradition order and approved it and it will go before the courts tomorrow," he added.
The United States will detail all allegations against Assange on Friday as he seeks his extradition in a London court.
United States Prosecutors originally charged Assange with a single bill for computer intrusion, but last month, 1
According to CNN's legal analyst Steve Vladeck, such a charge under the espionage law has never been successfully prosecuted.
Assange's first accusation gave rise to a debate over the first amendment and whether his alleged role in obtaining secret US material constituted protected journalistic activity.
Assange lived in Ecuador's Embassy in London for seven years until April when the country lifted its protection and he was arrested.
United Kingdom Home Office said in a statement: "Assange was arrested in connection with a provisional extradition request from the United States. He is accused of crimes involving abuse of computer and unauthorized disclosure of national defense information."  "We have received the complete extradition request, which has been certified by the home secretary.
" This case is now before the courts and it would be inappropriate to comment further. "