Such a military confrontation in the vital oil lanes of the Persian Gulf would be of major global concern. The warning builds on earlier threats by Iran to seal off the Gulf's strategic Strait of Hormuz — through which 40 percent of the world's oil passes — in response to any military attack.
"We have set aside 100 military vessels for each (US) warship to attack at the time of necessity," Gen. Morteza Saffari was quoted as saying by the conservative weekly Panjereh.
The US and Israel have said military force could be used if diplomacy fails to stop what they suspect is an Iranian nuclear weapons program. Iran denies any aim to develop such weapons and says its nuclear work is for peaceful purposes like power generation.
The US Navy's 5th Fleet headquarters is based just across the Gulf from Iran in Bahrain.
Saffari said more than 100 foreign warships were currently in the Persian Gulf and the Sea of Oman, adding that their sailors were "morsels" for Iran's military to target, the newspaper reported.
"Any moment the exalted supreme leader (Ayatollah Ali Khamenei) orders — or should the enemy carry out the smallest threat against (Iran's ruling) Islamic system — the Guard ... is ready for quick reaction," he was quoted as saying.
By putting the number of foreign warships at 100, the general appeared to suggest Iran has 10,000 military vessels at the ready. Iran is known to have many speed boats used by the Guard, but there is no public information about how many larger military vessels it has.
In January 2008, five small high-speed vessels believed to be from Iran's Revolutionary Guard briefly swarmed three US Navy ships passing near Iranian waters in the Gulf and delivered a radio threat to blow them up.
The war of words has intensified between Iran and the West since the UN Security Council imposed tougher sanctions last month in response to Iran's refusal to halt uranium enrichment, a technology that can be used to produce nuclear fuel or material for an atomic bomb.
Iran put its most powerful military force, the Revolutionary Guard, in charge of defending the country's territorial waters in the Persian Gulf in 2008.
"We believe the enemy, through extensive psychological warfare, wants to coerce us, but Iran ... is ready," said Saffari, who was the Guard's navy chief until early May.
"The enemy won't dare attack Iran."
