Koppel told The Hollywood Reporter he was serving as diplomatic correspondent for ABC News when Iranian revolutionaries raided the U.S. Embassy in Tehran and took 52 American hostages.
He also said he knew at the time six hostages were hiding out in the home of the Canadian ambassador, but said he didn't report the story out of fear for their safety.
"I got a call from the secretary of state, saying: 'I understand that you're going to put this story on the air tonight. And I can't tell you not to do it, but I would ask you not to, because it seems to us inevitable that if you put it on the air, that the Canadian Embassy would probably be taken, and that the Americans that escaped from the U.S. Embassy would probably be killed,'" Koppel recalled. "The only time in more than 50 years that I've ever killed a story."
Directed by and starring Ben Affleck, "Argo" is about how the six hostages made it home by pretending to be members of a Canadian film crew.