Iranian supreme leader Ayatollah Ali Khamenei warned the US that "if you make a single mistake about Iran, the supply of energy will definitely be put in serious risk."
The remarks came as EU foreign policy chief Javier Solana prepared to travel to Iran to deliver a package designed to convince Tehran to stop enriching uranium.
The package, agreed to last week by the five permanent members of the UN Security Council and Germany, warns of UN sanctions if Tehran continues its nuclear program, which the West fears is a cover for producing nuclear weapons.
It also includes an offer by the Bush administration to involve US officials in direct talks with Iran if it halts nuclear fuel production.
Iran, which pumps 3.85 million barrels a day of oil alone, is strategically located to shut off exports of about 17 million barrels a day from the Gulf region through the Straits of Hormuz.
