The US has warned Iran that failure to co-operate with the UN's nuclear watchdog would constitute further proof of a secret nuclear weapons programme.
Tehran denies it has a nuclear weapons programme
The warning follows the adoption of a new resolution at the International Atomic Energy Agency (IAEA) giving Iran until 31 October to prove that it is not pursuing such a programme.
The move triggered a walk-out by Iranian diplomats at the IAEA meeting in protest - and a threat that Tehran would conduct a "deep review" of its relations with the nuclear watchdog.
Iranian Foreign Minister
Kamal Kharrazi told reporters in Sarajevo, Bosnia, any resolution coming down hard on his country, "could make the situation more
Former Iranian president Akbar Hashemi Rafsanjani said Iran should not be compelled to agree
to intrusive inspections of its atomic programme.
"They are putting pressure on Iran to sign the Additional Protocol immediately and implement it."
"Accepting the Additional Protocol is not compulsory and no country has to accept," he told a prayer meeting.
Friday's resolution does not outline consequences of Iranian non-compliance, but leaves open the possibility of UN Security Council involvement.
A spokesman for the US state department said: "If Iran fails to take those steps by the deadline, that
would constitute further evidence of its ongoing efforts to conceal its clandestine activities.
"Unless Iran immediately reverses course, [the IAEA would be obliged] to report Iran's non-compliance to the UN Security Council," Adam Ereli said.
IAEA Director General Mohamed ElBaradei said the agency would adopt "a very vigorous approach to complete our work and we will make sure we get all the information we need".
Iran has some serious decisions to take and time is running out, says the BBC's Tehran correspondent Jim Muir.
It can suspend co-operation with the IAEA and adopt a stance similar to North Korea's - as some hardliners advocate.
Or it can open up fully to the inspectors, to prove it is not building nuclear weapons, our correspondent says.
The United States has accused Iran of covertly developing nuclear weapons under the guise of a nuclear energy programme.
But Iran says it is only seeking to produce low-grade uranium fuel to meet its energy needs.
The 35-nation governing board of the IAEA has been meeting all week, examining a report by IAEA inspectors, which says traces of weapons-grade uranium were found at an Iranian nuclear plant.
Friday's resolution calls on Iran to halt all further uranium enrichment activities.
Iran's ambassador to the IAEA, Ali Akbar Salehi, said Tehran would not accept any deadlines.
"You can't impose deadlines on a sovereign country," he said.
He accused the US of having territorial ambitions on the region.
"It is no secret that the current US administration, or at least its influential circle, entertains the idea of invasion of yet another territory, as they aim to re-engineer and re-shape the entire Middle East region."
The IAEA will decide the next step if it finds Iran has not co-operated when it meets again in November.