According to the newspaper, Berlusconi learned of the assassination plot through "reliable sources", though the prime minister did not elaborate.
Berlusconi said Gaddafi was not referring to his "political death", but to his physical death, the paper said.
"Because that's what he (Gaddafi) decided, he swore to this himself," Berlusconi was quoted as saying.
Libya has been rocked by fighting between pro- and anti-Gaddafi forces since February. An international military operation began in March following a UN resolution and has been extended till September.
Italy has been playing an active role in the military operation.