US President George W. Bush said last night the world must make clear to Iran that "we will not tolerate" its government building up a nuclear arsenal.
He also repeated US support for pro-democracy protests in Iran, which are now entering their ninth day.
Tehran, accusing Washington of interference by backing the protests, said the United Nations had tailored a damning report to suit the US view that Iran is using a civil power programme to obtain nuclear arms via the back door, a claim it denies.
A report by the UN's International Atomic Energy Agency (IAEA) that was debated in Vienna yesterday said Tehran had "failed to report certain nuclear material and activities," but was making amends.
The IAEA report said Iran repeatedly breached anti-nuclear treaties over the past 12 years by failing to declare the import, processing and storage of nuclear material.
Mr Bush said: "The international community must come together to make it very clear to Iran that we will not tolerate construction of a nuclear weapon".
But Iran's President Mohammad Khatami was adamant that Iran had no intention of building atomic weapons. "We announce that not only we do not want to obtain nuclear weapons but also we are among the ones who took the initiative in saying we want a region without nuclear weapons," he said.
Iran insists its nuclear programme is for peaceful civilian generation of electrical power but the United States believes Tehran wants a nuclear weapon. US officials question why Iran would need nuclear-generated power given its oil wealth.