WASHINGTON — Wikileaks founder Julian Assange will plead guilty to a felony charge in a deal with the Justice Department that will resolve a long-running legal saga that spanned multiple continents and centered on the publication of a trove of classified documents, according to court papers filed late Monday

Mr. Assange is scheduled to appear in the federal court in the Mariana Islands, an American commonwealth in the Western Pacific, to plead guilty to an Espionage Act charge of conspiring to unlawfully obtain and disseminate classified national defense information, the Justice Department said in a letter filed in court.

The guilty plea, which must be approved by a judge, brings an abrupt conclusion to a criminal case of international intrigue and to the American government’s years-long pursuit of a publisher whose hugely popular secret-sharing website made him a cause célèbre among many press freedom advocates who said he acted as a journalist to expose wrongdoing by the military.

Investigators, by contrast, have repeatedly asserted that his actions broke laws meant to protect sensitive information and put the country’s national security at risk.

He is expected to return to Australia after his plea and sentencing, which is scheduled for Wednesday morning, local time on Saipan, the largest island in the Mariana Islands.

The hearing is taking place there because of Mr. Assange’s opposition to traveling to the continental United States and the court’s proximity to Australia.