According to the report, Hariri taped the threat using a recording device concealed inside a pen. The device was given to Hariri by western security officials.
The report also states that Hariri managed to deliver copies of the recording before his assassination on February 14, to U.S. President George W. Bush, French President Jacques Chirac, and Pakistani President Pervez Musharaff.
Lebanese opposition members and sources in the West claim Syria is directly responsible for the assassination.
If found credible, the tape will provide proof for Syria's possible involvement in the assassination.
'I can destroy you and Lebanon'
According to the report, Hariri recorded Assad during a private meeting between the two just one week before the Lebanese parliament decided - as a result of heavy pressures made by Syria - to change the Lebanese constitution and thus extend the term of President Emile Lahoud, Assad's ally.
Hariri, who objected to the extension of Lahoud's term, was explicitly threatened by President Assad.
"You should know that Lahoud's term will be extended in any case… I will not allow you to replace him with another person," the magazine quoted Assad's recording.
"You must remember I can destroy Lebanon and you yourself. If I am forced to leave Lebanon, I will leave ruin and destruction behind
According to the report, the sophisticated pen was given to Hariri by the French Security Services after he told his close friend Chirac he felt his life was in danger.