Iran has asserted its right to produce nuclear energy a day after the United Nations passed a resolution demanding it suspend uranium enrichment.
Iran says the motives behind its nuclear activities are peaceful
President Mahmoud Ahmadinejad said he would not bow to "the language of force and threats".
Speaking at a rally in the country's north, he said Iran had the right to use nuclear technology to produce fuel.
The UN Security Council has given Iran until 31 August to stop nuclear activities, or face possible sanctions.
"The Iranian people see taking advantage of technology to produce nuclear fuel for peaceful purposes as their right," Mr Ahmadinejad told a crowd in the town of Bojnurd.
"Those who think they can use the language of threats and force against Iran are mistaken."
"If they don't realise that now, one day they will learn it the hard way," he added.
The US and other nations have accused Iran of trying to develop nuclear weapons, but Iran says its motives are peaceful.
UN resolution 1696 was passed by 14 votes to one on Monday, with Qatar the lone dissenter.
It gives Iran until the end of August to suspend uranium enrichment and open its nuclear programme to international inspections.
If it does not comply, the council would consider adopting "appropriate measures" under Article 41 of Chapter 7 of the UN Charter, which relates to economic sanctions.
Russia and China argued against the specific mention of sanctions, and said the Council would have to hold further discussions on what steps to take should Iran fail to meet the deadline.
Iran's ambassador to the UN, Javad Zarif, rejected the move, saying the country's nuclear programme "poses no threat to international peace and security".