Iranian President Mahmoud Ahmadinejad has said that his country does not need nuclear weapons.
The news conference was the second of Ahmadinejad's presidency
At a rare news conference in Tehran, Mr Ahmadinejad said they were needed only by people who "want to solve everything through the use of force".
The president defended Tehran's recent move to restart nuclear research, which has sparked international condemnation.
Iran says it has a right to peaceful nuclear technology and denies that it is covertly seeking to develop weapons.
The US, UK, France and Germany are threatening to refer Iran to the United Nations Security Council, which could impose sanctions.
But the president said a referral would not end its nuclear plans.
"If they want to destroy the Iranian nation's rights by that course, they will not succeed," he said.
Tehran has said it will stop snap UN inspections of nuclear sites if its case is sent to the Council.
The crisis intensified this week when Iran removed seals at three nuclear facilities, ending a two-year freeze.
Mr Ahmadinejad told reporters Tehran pursued an active foreign policy which sought peace, based on justice.
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
He criticised the "double standards" of Western countries which already had nuclear weapons, and attacked "arrogant rulers" for causing suffering.
"Leaders who believe they can create peace for themselves by creating war for others are mistaken," he said.
A few had a "medieval mindset" and sought to deprive Iran of valuable technology, without evidence of wrongdoing, he added.
Mr Ahmadinejad sparked international outrage with his hardline stance towards Israel, following his election last June.
He repeated both his attacks and calls for a referendum for Palestinians to choose their future political fate.
"(Israelis) have no roots in Palestine and almost all are immigrants," he said.
"Let the nation of Palestine decide among themselves."
Western countries are now seeking to persuade other members of UN nuclear watchdog the International Atomic Energy Agency (IAEA) to agree to refer Iran to the Council.
European, Russian, Chinese and US officials are due to meet in London on Monday, when they are expected to set a date for the crucial IAEA meeting.
On Friday, US President George W Bush and German Chancellor Angela Merkel agreed that the crisis should be resolved through peaceful means.
Washington, Israel and many European powers distrust Iran, partly because it had kept its nuclear research secret for 18 years before it was revealed in 2002.
Since last August, Iran has resumed all nuclear activity apart from enrichment, which can produce fuel for power stations or, under certain conditions, for bombs.
Tehran has always said it has the right under the nuclear Non-Proliferation Treaty - which it has signed - to research nuclear energy for peaceful purposes.