LONDON — Julian Assange, the founder of WikiLeaks, must remain in prison until an extradition hearing next year, a judge in London ruled on Friday, citing a “history of absconding,” according to British news agencies.

Mr. Assange had been scheduled to be released next week, after serving a 50-week sentence for jumping bail in 2012 and taking refuge in Ecuador’s London embassy rather than accepting extradition to Sweden to face a rape accusation.

But he is wanted in the United States, where he faces charges of conspiracy to hack government computers, and of obtaining and publishing secret documents in 2010.

[Update: Sweden has dropped the inquiry into rape allegations against Julian Assange.]

Mr. Assange has also been under attack for WikiLeaks’ release during the 2016 U.S. presidential campaign of thousands of Democratic Party emails stolen by Russian hackers, in what investigators say was an effort to damage the presidential campaign of Hillary Clinton.