Iran's President Mahmoud Ahmadinejad has said his country will not submit to "bullying" over its nuclear programme.
Crowds cheered Ahmadinejad's speech at the Bushehr nuclear site
In a defiant speech broadcast on state TV, he said Iran would never give up its "right" to peaceful nuclear energy.
Hours earlier, US President Bush had said the world should not allow Iran to acquire nuclear weapons.
UK Foreign Secretary Jack Straw will meet his Iranian counterpart in London on Wednesday. He told the BBC he will warn him that Iran has one last chance.
Speaking to crowds at Bushehr, the site of his country's first nuclear reactor, Mr Ahmadinejad said: "I am telling those fake superpowers that the Iranian nation became independent 27 years ago and... on the nuclear case it will resist until fully achieving its rights."
He added: "Our nation cannot step back because of the bullying policies of some countries in the world."
Mr Ahmadinejad was speaking a day after the five permanent members of the UN Security Council - the UK, France, the US, China and Russia - plus Germany, agreed to ask the International Atomic Energy Agency (IAEA) to report Iran to the council over its nuclear ambitions.
The powers agreed the final text of the resolution on Wednesday.
They urge Iran to extend "indispensable and overdue" cooperation to the IAEA and help it "clarify possible activities which could have a military dimension".
President Bush, in his annual State of the Union address, put further pressure on Tehran.
"The Iranian government is defying the world with its nuclear ambitions, and the nations of the world must not permit the Iranian regime to gain nuclear weapons," he said.
Western powers are concerned about Iran's recent decision to resume research on uranium enrichment - a process that can lead to a nuclear weapons capability.
Iran says its programme is solely aimed at energy production.
Tehran has warned it will end snap UN inspections of its nuclear facilities from Saturday if the IAEA reports it to the Security Council, which can impose sanctions.
Mr Straw said that he intends to press Iranian Foreign Minister Manouchehr Mottaki on the nuclear issue when they meet on Wednesday.
"I shall be saying to him that he really needs to see this agreed position by the international community not as a threat but as...a final opportunity (for Iran) to put itself back on track," Mr Straw told BBC radio.
In his speech, Mr Ahmadinejad also countered criticism by the US president over Iran's human rights record, accusing Mr Bush of hypocrisy.
"Those whose arms are stained up to the elbow with the blood of other nations are now accusing us of violating human rights and freedoms," Mr Ahmadinejad told cheering crowds.
"The Iranian nation is the standard-bearer of freedom and human rights."
Mr Bush in his State of the Union address described Iran as a nation "held hostage by a small clerical elite that is isolating and repressing its people".