"The US will face three problems if it attacks Iran. Firstly, it does not know the volume of our response," said General Rahim Yahya Safavi, the new special military advisor to supreme leader Ali Khamenei.
Safavi also warned over how Iran's reaction to a US attack could affect Israel - Tehran's regional archfoe - and also crude oil supply from the world's fourth-largest producer.
"Secondly, it does not know what will happen to Israel and, thirdly, the United States does not know what will happen to the oil flow," he was quoted by the ISNA news agency as saying.
Washington has never ruled out taking military action against Tehran, and its tone has sharpened again over the past week, with President George W. Bush warning that Iran's atomic program could lead to a "nuclear holocaust."
Iran has always insisted it would never launch any attack against a foreign country, but has also warned of a crushing response to any aggression against its soil.
Tehran has an array of medium range missiles, and claims that its longer-range Shahab-3 missile has a reach of 2,000 kilometers (1,200 miles), which would put Israel and US bases on the Arabian Peninsula within reach.
President Mahmoud Ahmadinejad has dismissed the chance of any US attack against Iran, but influential former president Akbar Hashemi Rafsanjani has warned of the dangers still posed by the United States.
Iran's refusal to rule out using oil as a weapon has frequently rattled oil markets, which fear that any squeeze in supplies from the Organization of Petroleum Exporting Countries' number-two producer could cause a huge jump in prices.
There have also been fears that Iran could block the Strait of Hormuz, a vital channel for the transport of oil.
New Guard chief among kidnappers of US diplomats
Meanwhile, the official Iranian news agencies revealed in the past few days additional details from the resume of the new Revolutionary Guards commander appointed this week, Mohammed Ali Jafari.
According to the reports, Jafari was one of the students who took over the US Embassy in Tehran in 1979 and took American diplomats hostage.
The revelations on Jafari's past may be interpreted in the US as another provocation on the part of Iran and add to the tensions between the two countries. The diplomatic relations between Washington and Tehran were severed following the diplomats' kidnapping crisis, which lasted 444 days.
The dialogue between the two countries was resumed in the past year, but only as part of low-level talks on ways to stabilize the security situation in Iraq.
Following Iranian President Mahmoud Ahmadinejad's election, Western officials estimated that he had also taken part in the kidnapping and was involved in its planning. These estimated have not been verified.
According to the news agencies, Jafari served as a representative of the Islamic student union and was active in "occupying the spy nest in Tehran" – the name given to the US Embassy by Revolutionary Guards members.
It is possible Jafari and others who took part in the kidnapping were promoted due to their role in the affair.
Dudi Cohen contributed to this report