Western powers were drawing up plans Friday for tougher sanctions on Iran, despite the reluctance of Russia and Asia to take part, diplomatic pressure having failed to halt Tehran's nuclear drive.
"We have no other tools. The only alternative would be to make concessions, and we're not ready to do that," said a senior French official, ruling out the option of military strikes pushed by some hawks in Washington and Israel.
Iran revived its nuclear programme in 2005, and the West has been trying to halt it ever since, alternating offers of talks with threats of isolation and slowly toughening up an array of unilateral and international sanctions.
The Iranian programme, which the West believes is designed to produce a nuclear weapon, has also been hit with a series of assassinations of its scientists and cyber-attacks on its computers.
But Tehran -- which insists it is merely seeking to generate nuclear power and develop medical isotopes -- has ploughed on defiantly, ratcheting up its enrichment of uranium from 3.5 percent, through 4.8 to 20 percent.
"There is no plausible justification for this production," US Secretary of State Hillary Clinton said this week, urging Tehran to "immediately cease uranium enrichment and to comply with its international nuclear obligations."
Once uranium is enriched to 90 percent it can be used to make an atomic bomb. Iran has moved some of its enrichment into an underground site, where it hopes it would be protected from eventual US or Israeli air strikes.
In parallel it has stepped up its ballistic missile programme, which could one day be ready to carry a nuclear warhead, and threats to disrupt oil shipping in the strategic sea lanes of the Strait of Hormuz.
The United Nations has agreed four packages of international sanctions in 2006, 2007, 2008 and 2010. Britain and the United States have recently also imposed tougher financial and trade sanctions of their own.
Now the European Union is on the point of stepping up its action, but Russia, China and Japan have been less enthusiastic. Asia's energy-hungry powers fear soaring prices if Iranian oil is embargoed.
Japan initially appeared willing to back its traditional Western allies, but on Friday began to backtrack, with Foreign Minister Koichiro Gemba saying: "We must look at this extremely carefully."
Russia warned Friday that any oil embargo would be seen as an attempt to force regime change in Iran, rather than as a bid to halt enrichment.
European diplomatic officials insist new sanctions would be aimed at forcing Tehran back to the negotiating table, even if they privately admit that they have so far failed to make any progress in this direction.
Citing Iran's decision to begin underground enrichment in a bunker complex in Fordo, south of Tehran, one European official said: "The Iranians have shifted to a policy of protecting their nuclear programme."
Nevertheless, officials insist that sanctions have had some effect.
"Iran wanted 50,000 centrifuges. They've only got 8,000 and only 6,300 in working order," said one, speaking on condition of anonymity.
"Iranian oil production is dropping, while it's going up everywhere else," another diplomat added, claiming financial sanctions have hit Iran's ability to insure oil cargoes and pushed its oil export price up 25 percent.
But the recession-hit West no longer dominates international relations like it did at the start of the crisis in 2005. Rising economic powers also have a role to play, and will defend their interests.
Iran's giant neighbour Turkey says it will not feel bound by any sanctions unless they are endorsed by the UN Security Council, and India says it had no intention of reducing its imports of Iranian crude.
Diplomats in Vienna said Friday that a high-level UN nuclear agency team will visit Iran late this month in another bid to clear up claims of covert weapons activities.