WASHINGTON — 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.