Amir Ali Hajizadeh, a brigadier general in the Islamic Revolutionary Guard Corps, made the comments to Iran's state-run Arabic language Al-Alam television, according to a report on the network's website.
"Iran will not start any war but it could launch a pre-emptive attack if it was sure that the enemies are putting the final touches to attack it," Al-Alam said, paraphrasing the military commander.
Hajizadeh said any attack on Iranian soil could trigger "World War Three".
"We can not imagine the Zionist regime starting a war without America's support. Therefore, in case of a war, we will get into a war with both of them and we will certainly get into a conflict with American bases," he said
"In that case, unpredictable and unmanageable things would happen and it could turn into a World War Three."
Prime Minister Benjamin Netanyahu has made increasing hints that Israel could strike Iran's nuclear sites and has criticised U.S. President Barack Obama's position that sanctions and diplomacy should be given more time to stop Iran getting the atomic bomb.
Tehran denied it is seeking weapons capability and says its atomic work is peaceful, aimed at generating electricity.