"There's an extradition request from the United States that is before the courts tomorrow", he told Radio 4's Today programme.
Sweden also seeks him for questioning about an alleged rape, which Mr Assange has denied.
He is serving a 50-week sentence in London's Belmarsh Prison for jumping bail in Britain.
Javid said that part of his role to sign all legitimate extradition requests, but Assange's fate was largely out of his hands.
Curiously, Home Secretary Javid signed the extradition paperwork despite not being on the best terms with the USA government right now.
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He went on to say: 'I am aware that I am an important player for the team but I hope they let me leave . Now it's a matter of getting out for the details.
WikiLeaks founder Julian Assange gestures from the window of a prison van as he is driven out of Southwark Crown Court in London on May 1, 2019. A Swedish court ruled earlier this month that Assange should not be detained in absentia, the first move under Swedish law that would have paved the way for his extradition.
It also published thousands of entirely unredacted U.S. diplomatic cables, exposing the nation's foreign policy workings and causing it severe embarrassment in the process.
The 47-year-old was due to appear before Westminister Magistrates' Court via video-link on May 30, but was too unwell.
"We have received the full extradition request, which has been certified by the Home Secretary".
When Assange fled to the Ecuadorean embassy, he said he feared he would be ultimately extradited to the United States where he had caused anger by publishing hundreds of thousands of secret USA diplomatic cables.
He insisted that Assange's supporters would "never give up" the fight to stop his extradition to the U.S. and secure his safe release from United Kingdom custody. A judge decides whether there is "prima facie evidence of guilt" and whether extradition would breach a person's human rights.
The 18 charges against Mr Assange reject his claim he was simply a publisher receiving leaked material - which would be protected under press freedom legislation.