VIENNA- Allegations that Iran was experimenting to make a nuclear bomb will take centre stage at the UN atomic watchdog's week-long autumn meeting, beginning Monday.
The International Atomic Energy Agency's 35-member board of governors will convene for its traditional September meeting.
At the same time, Iran says that Washington's intelligence on the alleged weaponisation studies is forged.
"The government of the United States has not handed over original documents to the agency since it does not in fact have any authenticated document and all it has are forged documents," Iran's envoy to the IAEA, Ali Asghar Soltanieh wrote in a confidential letter to IAEA chief Mohamed ElBaradei.
"Considering that there are no authentic documents on these alleged studies, there is no credible evidence of link between such forged claims and Iran."
And Soltanieh accused "the ambassadors of the United States, France and the United Kingdom ... of ill will and political motivation".
Iran has repeatedly dismissed the allegations as "baseless" and the evidence used to back up the charges as "fabricated".
In any case, it was "more important to concentrate energy on" what the IAEA has already presented, a senior western diplomat said.
In his latest report on the IAEA's six-year investigation into Iran's controversial programme, ElBaradei complained that one of the main sticking points remains Tehran's refusal to cooperate on the issue of the so-called alleged studies.
"Regrettably, the agency has not been able to engage Iran in any substantive discussions about these outstanding issues for over a year," ElBaradei stated in his latest report.
Iran nevertheless saw the new report as "positive", saying it testified to "the new approach of the Islamic republic."
The report did indeed note a reduction in the number of centrifuges actively enriching uranium at the enrichment plant in Natanz and Tehran's agreement to tighter monitoring at the plant.
Furthermore, Iran has also granted UN inspectors access to a research reactor in Arak.
The IAEA board will also hear allegations -- made first by Israel and more recently by France -- that ElBaradei is holding back key parts of his report on Iran.
A foreign intelligence said that the paper in question was a "thick document".
But a number of other diplomats, as well as sources within the IAEA, were sceptical whether such an annex really existed.
And ElBaradei has called the nuclear threat from Iran "hyped."
Iran insists it has the right to develop nuclear technology, which it says is aimed at generating energy for its growing population.
Israel is the only country in the Middle Ease that actually has nuclear weapons.
Observers say due the strong Jewish and pro-Israel lobbies in the US and some European countries, these countries have taken a hypocritical stance in relation to nuclear issues in the region.
Tehran had repeatedly protested against Israeli war threats, warning that it would retaliate in the event of any strike against Iran.