Iran's top nuclear negotiator, Ali Larijani, says his country is ready to compromise over its nuclear programme.
Iran could face sanctions if it is brought before the UN
He told the BBC that Iran was willing to discuss concerns about an alleged weapons programme and offer guarantees.
However, the US and EU said there was no point in further negotiations unless Iran offered fresh proposals.
The UN's atomic watchdog, the IAEA, will hold an emergency meeting on 2 February to discuss whether to refer Iran to the UN Security Council.
Iran denies US and European allegations that it is seeking to build nuclear weapons, claiming it wants the technology for energy purposes alone.
The nuclear activity which Iran has resumed is part of a process which could ultimately be used both to generate electricity and to make nuclear weapons.
Asked whether there were any circumstances in which Iran would suspend enrichment research, Mr Larijani said there were not.
"They should not ask a brave nation with very good scientists to expect not to engage in nuclear research," he said in an interview with BBC Tehran correspondent Frances Harrison.
However, he called for a resumption of talks in search for a compromise.
"If they want guarantees of no diversion of nuclear fuel we can reach a formula acceptable to both sides in talks."
However US Secretary of State Condoleezza Rice said there was "not much to talk about".
She said the EU had made clear Iran had crossed an important threshold.
IRAN'S NUCLEAR STANDOFF
Sept 2002: Work begins on Iran's first reactor at Bushehr
Dec 2002: Satellites reveal Arak and Natanz sites, triggering IAEA inspections
Nov 2003: Iran suspends uranium enrichment and allows tougher inspections
June 2004: IAEA rebukes Iran for not fully co-operating
Nov 2004: Iran suspends enrichment under deal with EU
Aug 2005: Iran rejects EU plan and re-opens Isfahan plant
Jan 2006: Iran re-opens Natanz facility
"Iran must not be allowed to get a nuclear weapon. It must not be allowed to pursue activities that might lead to a nuclear weapon and on that we are fully united," she said.
France, Germany and the UK have been circulating a draft IAEA (International Atomic Energy Agency) resolution referring Iran to the UN Security Council, which can apply sanctions.
While the US is likely to join European powers in pushing for referral, China and Russia opposed stern measures against Iran at talks on Monday.
Russia says a compromise offer is still on the table, and China has urged all parties to continue negotiations.
Both countries hold the power to veto resolutions at the UN Security Council.
Iranian President Mahmoud Ahmadinejad said it was clear the West's threats were "politically motivated".
"We are asking them to step down from their ivory towers and act with a little logic," he said.