"Nobody in the world will be able to bear the consequences of any action that is not peaceful because it would not result in a solution but in a disaster," Assad said after meeting French President Nicolas Sarkozy in the Syrian capital.
"Iran having the atom bomb is a threat to peace in the region and to peace in the world. Everyone must get the message across in their own way," Sarkozy told reporters.
Iran says its nuclear programme is for peaceful purposes. But the United States and Israel have not ruled out military action if the dispute cannot be resolved through diplomacy.
Defense Minister Ehud Barak repeated that view on Wednesday, saying in an interview there was still time for diplomacy but Israel was serious about using "any option" if it failed.
France has promised Assad economic incentives in return for political progress. It also wants Syria to break its alliance with Iran, but Assad has shown no sign he is willing to do so.
Syrian officials say Syria has been negotiating a preliminary deal to buy Airbus jets despite US sanctions on the Damascus government.