Documents revealed last week that appear to show Tehran is working on a nuclear bomb trigger were "forged" by Washington, Iranian President Mahmoud Ahmadinejad has told a US news network.

"They are all fabricated bunch of papers continuously being forged and disseminated by the American government," Ahmadinejad told ABC News in an interview aired Monday when asked about the confidential documents first revealed in London's The Times newspaper.

The obtained documents describe a four-year plan to test a neutron initiator, the component of a nuclear bomb that triggers an explosion.

The Times claimed that foreign intelligence agencies dated the documents to early 2007 -- four years after Tehran was thought to have suspended its weapons programme.

Describing charges that Iran's is continuing work on a clandestine nuclear weapons program as "a repetitive and tasteless joke," Ahmadinejad said the reports were about a nuclear trigger were "fundamentally not true."

US President Barack Obama's senior advisor David Axelrod said Sunday that any accusation of Washington fabricating documents was "nonsense."

"Nobody has any illusions about what the intent of the Iranian government is," Axelrod told ABC's "This Week."

"We've given them an opportunity to prove otherwise by allowing them to ship their nuclear material out to be reprocessed for peaceful use. And they have passed on that deal so far."

Ahmadinejad told AFP on Friday that Iran was ready to strike a uranium enrichment deal if the United States and the West respect the Islamic Republic and stop making threats.

Iran is under three sets of UN sanctions for refusing to suspend 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 the reactor.

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