Iran has threatened to press ahead with industrial-scale uranium enrichment if its nuclear work is referred to the UN Security Council.
Iran says its nuclear programme is purely peaceful
Nuclear negotiator Ali Larijani said Iran would "pursue its own path" if the US and its allies "want to use force".
He was speaking a day before the UN nuclear watchdog meets in Vienna.
Western powers believe Iran wants to develop nuclear weapons, for which enrichment is a key process, but Tehran says its plans are for civilian energy.
Mr Larijani told a news conference in Tehran: "If Iran's nuclear dossier is referred to the UN Security Council, [large-scale] uranium enrichment will be resumed.
"If [the US and its allies] want to use force, we will pursue our own path."
Mr Larijani added: "Going to the Security Council will certainly not make Iran go back on research and development."
Mr Larijani said Iran had no interest in using oil prices as a weapon against the West but warned that if action was taken against Tehran, it would affect international oil prices anyway.
The UN watchdog - the International Atomic Energy Agency (IAEA) - is beginning on Monday a meeting that will discuss a report on Iran by the agency's director general, Mohammed ElBaradei.
The report, which was leaked to the media earlier this week, says the Iranians have begun feeding uranium gas into centrifuges - a first step in a process that can produce fuel for nuclear reactors or bomb material.
It also says Tehran has rejected stricter inspections, falling back on the regular regime under the Nuclear Non-Proliferation Treaty.
The IAEA's board of governors is expected to confirm its 4 February decision to report Iran to the Security Council - which can in turn impose sanctions.
However BBC world affairs correspondent Paul Reynolds says sanctions are still a long way off and might never come.
Warning and demands that Iran should suspend its nuclear programme will in any case come first, our correspondent adds.
Russian and China - permanent members of the Security Council with the power of veto - have so far opposed imposing sanctions on Iran.
Iranian media on Sunday reported small-scale protests in support of the national nuclear programme in several cities, including Tehran, Shiraz, Yazd and Ahvaz.
Iran announced in January that it was resuming uranium enrichment research, ending a two-year-old suspension it had agreed to with the UK, France and Germany.