The Justice Department is weighing anew whether to charge Julian Assange, the founder of WikiLeaks, for his role in the disclosure of highly classified information that the United States government claims has harmed national security and diplomatic relations, a law enforcement official said.
The debate among prosecutors, which the official described as vigorous, is being fueled by Attorney General Jeff Sessions, who said at a news conference Thursday that arresting Mr. Assange was a priority for the Justice Department.
The official, speaking on the condition of anonymity because the details of the discussions remain secret, said senior Justice Department officials had been pressuring prosecutors in the Eastern District of Virginia to outline an array of possible charges.
But the official said prosecutors were skeptical that they could pursue the most serious charges, of espionage, with regard to the documents Mr. Assange disclosed years ago with the help of an Army intelligence analyst, Chelsea Manning. Ms. Manning was convicted and sent to prison, but President Barack Obama commuted her sentence in January.
A lesser charge could be theft of government documents, but the official said prosecutors wanted, ideally, to pursue more serious counts against Mr. Assange, who has sought refuge in the Ecuadorean Embassy in London since 2012 to avoid extradition to Sweden on accusations of rape.
A Justice Department spokeswoman declined to comment on Thursday.
Mr. Assange says he is a journalist whose work is no different from that of major news organizations. This claim could complicate a prosecution and put the Justice Department at odds with the news media, which also seeks to obtain and publish government secrets.
“Never in the history of this country has a publisher been prosecuted for presenting truthful information to the public,” said Ben Wizner, director of the American Civil Liberties Union’s Speech, Privacy and Technology Project. “Any prosecution of WikiLeaks for publishing government secrets would set a dangerous precedent that the Trump administration would surely use to target other news organizations.”
Charges would also highlight the fact that President Trump praised WikiLeaks during the 2016 campaign for publishing prominent Democrats’ emails, hacked by Russian intelligence. And arresting Mr. Assange and bringing him to the United States to stand trial would be difficult.
WikiLeaks released a trove of C.I.A. documents last month that described sophisticated software and techniques to break into electronics. The disclosure was said to infuriate C.I.A. officials, and it put pressure on the Justice Department to prosecute Mr. Assange.
Mr. Sessions is not the first Trump administration official to go after Mr. Assange publicly, signaling that the White House intends to take a hard line against leakers. Last week, the C.I.A. director, Mike Pompeo, said that “WikiLeaks walks like a hostile intelligence service and talks like a hostile intelligence service.” But he, too, applauded the disclosures of WikiLeaks when they benefited Mr. Trump during the campaign.
Officials have said the F.B.I. supports prosecuting Mr. Assange. Several years ago, it sent a series of documents to the Justice Department outlining charges that investigators said they had evidence to support. At the time, F.B.I. counterintelligence agents believed charging Mr. Assange would deter him from posting new troves of American documents.
The Justice Department, then run by Obama appointees, declined to move forward.