The head of the UN's nuclear watchdog says the row over Iran's nuclear research is reaching a critical phase.
Iran threatens to resume nuclear enrichment
But Mohamed ElBaradei said the issue was not yet at crisis point, and Tehran had a "window of opportunity".
The watchdog body, the International Atomic Energy Agency (IAEA), is considering a call to report Iran to the UN Security Council.
Iran remains defiant, saying again it will curtail inspections and resume suspended activities if reported.
The board of the IAEA has been meeting in Vienna to decide on the proposed resolution by the five permanent Security Council members plus Germany that Iran's nuclear programme be referred.
President Ahmadinejad insists Iran has the right to nuclear power
The meeting broke up on Thursday without a vote and will be resumed on Friday.
Correspondents said an early vote had not been expected as many board members wanted to express their views.
In Washington, US intelligence chief John Negroponte has said Iran probably does not yet have the means to make a nuclear bomb.
"We judge that Tehran probably does not yet have a nuclear weapon and probably has not yet produced or acquired the necessary fissile material," he told the Senate Intelligence Committee.
Earlier, Mr ElBaradei said: "We are reaching a critical phase but it is not a crisis situation. It's about confidence-building and it is not about an imminent threat."
He said the Security Council members had made it clear no action that might lead to sanctions could take place before March, when he is to submit a conclusive report.
"All of them are saying that this is simply a continuation of diplomacy," Mr ElBaradei said.
Diplomats have said the 35-member board will easily pass the resolution, and Russia has re-affirmed its intention to back it after Iran insisted it had Moscow's support.
The six powers - Britain, the US, France, China, Russia and Germany - agreed the resolution on Monday.
It was however edited over the next two days, with Russia insisting it should not specifically refer to UN statutes that would authorise sanctions.
The US said it was supporting a compromise to show it wanted a political settlement and to build an international consensus on the issue.
Russia's chief delegate, Grigory Berdennikov, said: "We do not object to informing the Security Council of the United Nations about the work carried out by the agency in relation to Iran."
However Iran's ambassador to the IAEA, Ali Soltanieh, told the BBC earlier he was sure Russia and China would side with Iran.
The resolution urges Iran to extend "indispensable and overdue" co-operation to the IAEA and help it "clarify possible activities which could have a military dimension".
But Iran's chief nuclear negotiator, Ali Larijani, warned Mr ElBaradei on Thursday that if Tehran were reported then IAEA inspections would be "extensively limited" and "all the peaceful nuclear activities under voluntary suspension would be resumed without any restriction".
Iranian President Mahmoud Ahmadinejad also vowed his country would not give up its nuclear programme, including the sensitive issue of uranium enrichment.
"The Iranian people will follow their own path and will under no condition renounce their legitimate right," the official news agency IRNA quoted him as saying.
Iran recently decided to resume suspended research on uranium enrichment - a process that can lead to a nuclear weapons capability - raising concern among Western powers.
Iran says its programme is solely aimed at energy production.