There are reports that EU diplomats have finalised the terms of a new sanctions deal against Iran over its nuclear programme.
On the table is a total ban on European purchases of Iranian oil - a sanction which would not just hit Iran but key EU buyers including Greece, Italy and Spain.
Sanctions are already expected against Iran’s central bank.
Today’s crackdown follows the stepping up of economic and diplomatic sanctions against Iran last month, targeting members of the ruling regime and associates who are subject to visa bans in Europe and the freezing of assets.
But today’s ramping up of measures reflects concern that Iran is developing nuclear weapons under the guise of a nuclear energy programme.
Britain's Foreign Secretary William Hague has urged Iran today to “come to its senses” and resume negotiations on its nuclear programme.
He said an EU oil embargo due to be formally agreed against the regime within hours was part of “peaceful and legitimate” measures and not designed to trigger conflict.
Any bid by Iran to block the Strait of Hormuz at the entrance to the Gulf, through which 20% of the world’s oil exports pass would be “illegal” and “unsuccessful”, Mr Hague warned.
Mr Hague commented: “These (sanctions) are peaceful and legitimate measures. They are not about conflict.
“I hope Iran will come to its senses on this issue and agree to negotiate.”
He added: “Any attempt to close the Strait of Hormuz would be illegal, and I believe would be unsuccessful.”
Yesterday, in the wake of Iranian threats to close the Strait, the American aircraft carrier USS Abraham Lincoln passed through it and is now in the Gulf.
EU governments are calculating that the loss of European oil markets will persuade Iran to reopen talks on its nuclear plans.
But any ban would be phased in over months, not least to ease the impact on EU nations facing economic difficulties and which are very dependent on Iranian oil.
The UK, Germany, France and the Netherlands have been leading calls for nothing more than a three-month delay before the sanctions bite, but Greece, which fears its economic woes will worsen if it cannot find alternative suppliers at Iran-style preferential rates – has urged a much longer phase-in to ease the pain.