Iran may stop allowing snap inspections of its nuclear facilities if it is referred to the UN Security Council, says the country's top negotiator.
Iran resumed its uranium conversion work in August
Ali Larijani said Tehran would also consider pulling out of the nuclear non-proliferation treaty (NPT) if the "language of force" continues.
The UN nuclear watchdog, the IAEA, is discussing Tehran's activities, which Iran insists are for peaceful purposes.
The US and the EU are calling for Iran to be referred to the Security Council.
If that happens, Tehran would review the additional NPT protocol that allows international inspections of its nuclear sites to be carried out at short notice, said Mr Larijani.
The chief nuclear negotiator sounded angry as he complained that Europe and the world were looking to insult Iran and treat its people as second class citizens, the BBC's Frances Harrison reports.
He warned that it was not a good idea to confront the Iranian nation, and said dialogue was a better way forward.
"We don't want the path to become more difficult," he said.
"But if you want to use the language of force, Iran will be left with no choice, in order to preserve its technical achievements, to get out of the framework of the NPT and out of the framework of the additional protocol, and resume enrichment."
Earlier, Iran's Supreme Leader, Ayatollah Ali Khamenei, said in a speech on state television that Tehran would "not surrender to any sort of pressure and threat".
He was speaking as the three EU countries that had led nuclear negotiations with Iran called for Security Council involvement on the issue.
France, Britain and Germany have circulated a rough draft of a resolution to members of the IAEA (International Atomic Energy Agency) board of governors.
The draft, according to a copy obtained by Reuters news agency, urges the IAEA to report "Iran's many failures and breaches of its obligations to comply" with the NPT.
The US ambassador to the IAEA, Greg Schulte, said on Monday: "Our goal... remains to achieve a diplomatic solution".
"But this will require Iran to change its course and to co-operate fully with the IAEA to cease its conversion activities and to go back to the negotiating table," he told the BBC.
But key members of the 35-member board, including Russia, oppose Security Council intervention.
Russia has reportedly asked the EU to delay referral, with Foreign Minister Sergei Lavrov making the appeal on the sidelines of the UN General Assembly meeting in New York.
Iran, which resumed its sensitive uranium conversion work in August, insists it has an "inalienable right" to produce nuclear energy.
In a speech to the UN General Assembly on Saturday, President Mahmoud Ahmadinejad said Iran's programme was entirely legal and attacked what he called a "nuclear apartheid" that permits some countries to enrich fuel, but not others.
The US and EU took the speech as a rejection of negotiations and incentives they offered to Iran to give up its nuclear programme.