Iran has warned it will end snap UN inspections of its nuclear facilities from Saturday if a decision is made to report it to the UN Security Council.
Iran insists its nuclear programme is solely for peaceful purposes
It comes after six key powers said the UN's nuclear watchdog, which meets on Thursday, should take Iran to the UN.
The nuclear agency has confirmed that Iran has started preparations to resume producing enriched uranium, which can be used in nuclear weapons.
Iran denies US-led claims that it is seeking to develop nuclear arms.
Tehran also warned on Tuesday that it will resume uranium enrichment if it is reported to the Security Council, which has the power to impose sanctions.
The nuclear crisis has intensified since Iran resumed nuclear activity last summer after a two-and-a-half year freeze.
Iranian Foreign Minister Manouchehr Mottaki said Iran would take decisive action if the International Atomic Energy Agency (IAEA) sends the issue to the UN.
"If it happens, the government will be required under the law to end the suspension of all nuclear activities it has voluntarily halted.
"The first victim will be the Additional Protocol [of the Nuclear Non-proliferation Treaty (NPT)]. If it happens, Iran will definitely terminate its co-operation [with the IAEA] as of Saturday, 4 February," he said on Iranian television.
The Additional Protocol allows UN inspectors to carry out surprise inspections of nuclear sites or sites which are deemed to be suspect.
In its report released ahead of the IAEA governors crisis meeting on Thursday, the nuclear watchdog said Iran had not yet resumed uranium enrichment but had begun renovation work at its Natanz plant.
Iran removed UN seals at the facility on 9 January, spurring the international community to call for the involvement of the Security Council for the first time.
The IAEA brief also said the agency had seen an Iranian document which can only be used in making nuclear weapons parts.
Iran said it had not asked for the document, which it received from the black market network in nuclear weapons, run by Pakistani scientist A Q Khan.
In addition, the report said Iran had declined to answer questions about tests related to high explosives which could have a military dimension.
All five permanent members of the UN Security Council - the UK, France, the US, China and Russia - plus Germany, agreed on Tuesday to ask the IAEA to report Iran to the council.
However they said the council should take no action until March, after it had received a report on Iran's nuclear programme from the IAEA.
Russia and Iran are due to resume talks in February over a Russian plan to enrich Iranian uranium on Russian soil.