But UN chief Kofi Annan said after a phone conversation with a top Iranian nuclear negotiator that Tehran was still interested in pursuing talks with European nations despite its decision to resume sensitive nuclear fuel work.
Mr Annan said Iran's top nuclear negotiator, Ali Larijani, told him that the Iranians "are interested in serious and constructive negotiation but within a time frame."
Speaking after a crisis meeting in Berlin, the foreign ministers of
Britain, France and Germany called for an emergency meeting of the UN nuclear watchdog to refer the dossier to the world body's executive.
Hectic diplomacy
In Washington, US Secretary of State Condoleezza Rice accused Tehran of a "deliberate escalation" of the dispute and said it was in "dangerous defiance of the entire international community."
She said the Security Council should "call for the Iranian regime to step away from its nuclear weapons ambitions."
The coordinated statements usher in a period of hectic diplomacy as Europe and the US seek to build support for some kind of intervention by the Security Council, which alone can impose UN sanctions.
UN chief Kofi Annan spoke with Iran's top nuclear negotiator Ali Larijani, UN spokesman Stephane Dujarric said, but he gave no details of what was said during the 40-minute telephone conversation.
It follows a storm of international criticism after Iran broke the seals at three nuclear plants in order to resume research on uranium enrichment.
"We believe the time has now come for the Security Council to become involved to reinforce the authority of IAEA resolutions," the European trio said, referring to the International Atomic Energy Agency.
"We will, therefore, be calling for an extraordinary IAEA board meeting with a view for it to take the necessary action to that end."
"The talks with Iran are at a dead end," Germany's Frank-Walter Steinmeier told a news conference.
But a senior Iranian nuclear official said Tehran was unperturbed.
"We should not be worried," said Abdolreza Rahmani Fazli, the deputy to Ali Larijani who is Iran's chief official for the nuclear file.
"It is not what we want, but if that's the case ... our officials must plan their policy ... to put on a strong show of diplomacy and make our case," he said.
Weapons fears
Western suspicions that Iran is secretly trying to develop nuclear weapons have been strongly denied by Tehran, which says its program is for peaceful purposes.
Enriched uranium can be used as fuel for nuclear power stations, but in its highly enriched form makes the explosive core for atomic weapons.
The joint statement by Steinmeier, British Foreign Secretary Jack Straw and France's Philippe Douste-Blazy cited Iran's "documented record of concealment and deception."
The Islamic republic "seems intent on turning its back on better relations with the international community," it added.
Its decision to restart enrichment activity was "a clear rejection" of the talks process and "constitutes a further challenge to the authority of the IAEA and international community."
A European official in Berlin said the IAEA's governors could be convened "in the coming weeks" but declined to give more details.
"What we want to do is use the authority and weight of the Security Council to bring home to Iran the importance of abiding by the resolution of the IAEA," he said. "Don't expect us to move straight to sanctions."
Sanction options
In lieu of sanctions, the official suggested as one option that the United Nations could impose a mandatory suspension of uranium enrichment activities which Tehran had previously suspended voluntarily.
IAEA director Mohamed ElBaradei has said Iran plans to start "small-scale" enrichment at Natanz, one of the sites where seals were broken.
Mr Ahmadinejad insisted Tehran would press ahead.
"Today, those who have the highest level of nuclear energy have the nuclear fuel in their claws, and are using it as an economic and political weapon," national television quoted him as saying.
"In these circumstances we must master the fuel cycle and the peaceful nuclear technology."
Officials from the so-called EU-3 plus China, Russia and the United States will meet next week in London for more talks.
In Moscow, Russian Foreign Minister Sergei Lavrov said Iran's actions fed suspicions that its program "could have a hidden military aspect," while a Chinese foreign ministry spokesman voiced concern and urged Tehran to resume dialogue.
Although US Vice President Dick Cheney spoke Wednesday of sanctions, there is no immediate word on what Washington has in mind, nor whether it can muster enough UN backing, notably from China and Russia which have shown little past inclination to order punitive action.