Iran has warned it will attack Israel in response to any "evil" act by the United States as the row over the Gulf state's nuclear programme continued today.
The Iranians separately said it had brought its uranium enrichment programme to a level close to the maximum required for power generation.
Iran's defiance comes shortly before world powers meet in Paris today to discuss Tehran's rejection of a United Nations call to halt uranium enrichment.
Senior officials from the UN Security Council's permanent members - Britain, China, France, Russia and the United States - plus Germany are due to discuss how to curb an Iranian programme that could produce material for use in nuclear warheads.
The United States, Britain and France are expected to introduce a resolution to the Security Council this week that would legally oblige Iran to comply with UN demands.
The three countries favour limited sanctions if Tehran remains defiant. Iran said Russia and China, also veto-wielding permanent council members, would not back any punitive measures.
Nicholas Burns, the US under-secretary of state for political affairs, said in Paris that today's meeting would seek to keep the Security Council members and Germany united before a meeting of foreign ministers in New York on May 9th.
He said he expected a consensus to emerge over the next 30-40 days on the need to send a "stiff message" to Iran, adding that a range of sanctions had been discussed privately.
These included restricting exports to Iran of dual-use technology that could support its research and development or help it fabricate fissile material or a nuclear device.
Iran says its programme is needed for power generation and refuses to back down from what it calls its right to enrich uranium for peaceful purposes.
The head of Iran's Atomic Energy Organisation, Gholamreza Aghazadeh, today said his country had now succeeded in purifying uranium to 4.8 per cent, at the top end of the 3 to 5 per cent range for fuel used in nuclear power plants.
Iran has previously said it had enriched to more than 4 per cent, far below the 80 per cent level needed for bomb-making.
The United States and Israel are deeply concerned about Iran's potential capability and Washington has not excluded war if diplomacy fails.
Iran today said the US threat was a worry but nonetheless would not restrict its programme.
"We have announced that wherever America does something evil, the first place that we target will be Israel," ISNA quoted a senior Revolutionary Guard commander as saying today.
Iranian President Mahmoud Ahmadinejad previously called for the Israel to be "wiped off the map" though today Iran's deputy oil minister said "everybody is worried" about a possible US attack.