"Some countries are angry that our people defend their nuclear rights," foreign ministry spokesman Ramin Mehmanparast told reporters.

When Western powers "want to pressure us they craft such scenarios which is unacceptable," he said.

"This claim has political aims and it is psychological warfare which has no basis at the International Atomic Energy Agency," he added.

He was reacting to a report in the British newspaper The Times which said on Monday it had obtained notes describing a four-year plan by Iran to test a neutron initiator, the component of a nuclear bomb which triggers an explosion.

The Times reported that foreign intelligence agencies dated the documents to early 2007 -- four years after US agencies had previously assessed Iran had suspended efforts to produce a weapons.

It said the documents detailed a plan to test whether the device works -- without leaving traces of uranium that the outside world could detect.

Iran insists its nuclear programme is solely for civilian purposes and rejects Western suspicions that it is covertly trying to develop a bomb.

Iran is under three sets of UN sanctions for its refusal to suspend uranium enrichment and risks a further round after rejecting a UN-brokered deal to send its low enriched uranium abroad to be further refined into fuel for a research reactor.

Its enrichment work lies at the centre of Western concerns about its intentions as the process can produce fuel for nuclear reactors but in highly extended form can also be used to make the fissile core of an atomic bomb.