Iran's Supreme Leader Ayatollah
Ali Khamenei has warned that fuel shipments from the Gulf region could be disrupted if the US makes a "wrong move".
In a speech on state TV, Ayatollah Khamenei also said accusations
that Iran intended to make a nuclear bomb amounted to a "sheer lie".
He insisted Iran would not give up its right to produce nuclear fuel.
Tehran has agreed to study proposals drawn up by six world powers to defuse the row over Iran's nuclear programme.
The proposals are due to be delivered by the EU's foreign policy head, Javier Solana, within days.
The precise details of the proposals are not known, but they aim to persuade Iran to give up its nuclear work - a step which Iran has repeatedly said it will not take.