Published in the Libero newspaper on Saturday, Berlusconi said in the interview conducted on Christmas eve, that he had received "precise and verified news of an attack on Rome on Christmas Day. A hijacked plane above the Vatican... An attack from the sky."
"The threat from terrorism is extremely high at this moment. I've spent today (Dec 24) in Rome to deal with the situation," Berlusconi added.
"Now I'm calm. It will pass... I don't say this out of fatalism but because I am aware that our defences are very high. If that is what they have organised, they won't make it."
He gave no details of who was believed to be behind the planned attack or of any measures taken to prevent it.
No one was immediately available for comment at the prime minister's office or the interior ministry, which is in charge of national security.
At the Vatican, chief spokesman Joaquin Navarrro-Valls told Reuters: "As is customary, we do not comment on matters security".