"It will cost the United States and the planet dear," Assad said in an interview with France Inter radio, adding that such an attack, if it occurred, would have an impact on Israel.
"Israel will pay directly the price of this war. Iran has said so. The problem is not the action and reaction. The problem is that when one starts such action in the Middle East, one cannot manage the reactions that can spread out over years or even decades," he said.
Assad added that logic would dictate that there would be no attack on Iran because of the serious repercussions, but such reasoning was not necessarily shared by the current US Administration.
"This administration is an administration whose doctrine is a warmonger's doctrine. It does not reason with our logic, ours and that of most European countries, most countries in the world."
Iran denies Western charges that it is secretly trying to develop nuclear weapons under the cover of a civilian atomic program. Tehran says it only wants to master nuclear technology to generate electricity.