LONDON — A London court on Wednesday ordered the extradition of the WikiLeaks founder Julian Assange to the United States, the latest but not the last step in a long-running battle in British courtrooms.

The order to extradite Mr. Assange, who is being sought by the United States in connection with charges under the Espionage Act, must be signed by the British home secretary, Priti Patel, and Mr. Assange has four weeks to appeal to her directly.

The court decision, delivered in a brief hearing that saw Mr. Assange dial in by video call from a prison in London, was the latest blow to his attempts to fend off his extradition. Protesters, as they have done throughout his legal battle, gathered outside the courtroom in central London.

Britain’s Supreme Court ruled last month that Mr. Assange could not appeal an earlier decision that paved the way for his extradition, bouncing the decision back to the Westminster Magistrates’ Court, which made the decision on Wednesday.

Ms. Patel will now decide whether to order the extradition or refuse the request, but Mr. Assange’s defense team also is entitled to make submissions to her before her final decision is made. His legal team has until May 18 to do so. The Home Office did not immediately respond to a request for comment.

Mr. Assange was charged in the United States under the Espionage Act in connection with obtaining and publishing classified government documents about the wars in Afghanistan and Iraq on WikiLeaks in 2010. Those files were leaked by Chelsea Manning, a former military intelligence analyst.

Mr. Assange has waged a prolonged legal battle against his extradition following his arrest in London in 2019, after he spent seven years holed up inside the Ecuadorean Embassy in an effort to avoid detention.

His defenders have sought to present the case as a matter of press freedom, and his extradition to the United States could raise major issues about First Amendment rights, experts say.

“The extradition of Julian Assange would also be devastating for press freedom and for the public, who have a right to know what their governments are doing in their name,” said Agnès Callamard, Amnesty International’s secretary general.

She also said that decision placed Mr. Assange “at great risk of prison conditions that could result in irreversible harm to his physical and psychological well-being.”