US prosecutors are expected to request the extradition of a former Libyan intelligence officer over the bombing of Pan Am Flight 103 over Lockerbie in 1988.
Abu Agila Mohammad Masud is now suspected of making the bomb that blew up the plane and killed 270 people over the Scottish town.
The terrorist attack, the deadliest on British soil, predominantly killed Americans returning home for Christmas holidays.
The Justice Department is expected to unseal charges against Mr Masud in coming days, US media reported.
Mr Masud was previously in custody in Libya on unrelated charges but his exact whereabouts are unknown, The New York Times reported.
The suspect is alleged to have been a top bomb-maker for the Libyan dictator Muammar Qaddafi.
Scottish prosecutors previously identified Mr Masud, as well as Qaddafi's former spy chief, Abdullah Al Senussi, as suspects.
The case against Mr Masud in part relies on the work of investigative journalist Ken Dornstein. His brother David was among those killed on the London-New York flight.
Mr Dornstein said Mr Masud’s name had been mentioned in the Lockerbie investigation but authorities could not track him down.
He told BBC's Radio 4 Today programme: "I decided to revisit the records and see if I could find something that was overlooked.
“Masud is a case of someone whose name had been in the record but it wasn’t a name anyone could do anything with ... people thought it wasn’t a real person
“He was essentially a ghost, he was a phantom. There was no reason to be certain he existed.”
Mr Dornstein said a breakthrough for his investigation came when he discovered Mr Masud was associated with the bombing of Berlin’s La Belle nightclub in 1986.
“When I matched that up I released Masud wasn’t a ghost, he was a bomb expert,” he said.
“I found the one man who confessed to the La Belle bombing and he had named Masud.
“He was the only person in the world who admitted to knowing him and could tell me who he was. He told me further that Masud had told him in private meetings he had been involved in Lockerbie.
“He could confirm that Masud was still alive, which was news to me, and he could tell me where to find him – he was in a Libyan prison.”
Mr Dornstein said he was “pretty satisfied that Masud put together the bomb” that blew up the plane.
Libyan citizen Abdelbaset Al Megrahi, also an intelligence operative, is the only man to be convicted over the bombing, in 2001. He died in 2012.