Iran has defiantly rejected calls from the UN nuclear watchdog to suspend all its uranium enrichment activities.
Iran says no international body can force it to end enrichment
Tehran also vowed to block snap inspections of its nuclear sites if the issue is sent to the Security Council.
"Iran will not accept any obligation regarding the suspension of uranium enrichment," chief nuclear negotiator Hassan Rohani said.
Enriched uranium can be used to make nuclear weapons, but Iran insists its programme is for peaceful purposes.
"If they want to send Iran to the Security Council, it is not wise, and we will stop implementing the Additional Protocol," Mr Rohani told a news conference in Tehran after the decision by the International Atomic Energy Agency.
The Additional Protocol to the nuclear Non-Proliferation
Treaty allows snap nuclear checks.
"We are committed to the suspension of actual enrichment, but we have no decision to expand the suspension," Mr Rohani said.
"This demand is illegal and does not put any obligation on Iran. The IAEA board of governors has no right to make such a suspension obligatory for any
He said European countries were wrong in thinking Iran was only one step away from full enrichment; Iran was already at that point and could complete the nuclear fuel cycle "today" if it wanted.
And he added that, if Iran was referred to the UN Security Council for punitive action, it would consider pulling out of the Nuclear Non-Proliferation Treaty altogether.
Iran suspended enrichment a year ago as a confidence-building measure, but has continued activities such as building the centrifuges that refine the uranium.
The US has strong suspicions that Iran is using its nuclear programme to make weapons in secret.
Along with Israel, it is pushing the IAEA to refer Iran to the Security Council if it does not comply with the agency's demands. The Security Council could then impose sanctions.
"With every passing week, Iran moves that much closer to reaching the point where neither we, nor any other international body, will be able to prevent it from achieving nuclear weapons capacity," said chief US delegate Jackie Sanders on Saturday.
NUCLEAR NON-PROLIFERATION TREATY (NPT)
Aims to prevent spread of nuclear weapons and develop peaceful use of nuclear power
Ratified in 1970 by the US, UK and Russia (then Soviet Union)
China and France sign up in 1992
Some 190 "non-nuclear" countries - including Iran - have ratified the pact
They agree not to develop or acquire such weapons
Non-signatories India, Pakistan and Israel are known or believed to have nuclear arms
Nuclear experts have said the Parchin military complex, south-east of Tehran, may be a site for the research, testing and production of nuclear arms.
Iran says it has a right to enrich uranium as part of its peaceful nuclear programme, including power generation.
Iran also accused Britain, France and Germany of breaking an accord reached last year on Iran's co-operation with the IAEA.
The Board of Governors considers it necessary, to promote confidence, that Iran immediately suspend all enrichment-related activities
"The three Europeans have violated the terms of the accord regarding enrichment because the suspension of enrichment was voluntary," Mr Rohani said.
In its resolution, the IAEA said its board of governors had judged that an Iranian promise made to the three European nations last year to suspend uranium enrichment activities had fallen short of expectations.
The resolution called on Iran to suspend all uranium enrichment activities and asked Iran to grant access to its inspectors.
The IAEA board of governors is next set to meet on 25 November to review Iran's alleged nuclear weapons programme.
Iran has until then to answer all outstanding questions about its nuclear programme.