The one-and-half page unofficial text supplied to Washington by International Atomic Energy Agency chief Mohamed ElBaradei gives the IAEA's assessment that even reduced enrichment work would help Iran move towards "successful long-term sustained centrifuge operation", which is needed to make enriched uranium that can be used for nuclear power reactor fuel or nuclear bomb material.

The revelation of the document, which was drawn up in late May, comes as world powers await Iran's response to an offer of talks about its nuclear programme, which has raised fears Tehran is secretly developing nuclear weapons.

The talks, which offer trade and other benefits in return for Iran guaranteeing its nuclear program is peaceful, can only start if Iran suspends uranium enrichment.

On Sunday, Iran reiterated its stand against preconditions to launch talks, as Tehran says it has a right under the Non-Proliferation Treaty (NPT) to make nuclear reactor fuel for what it insists is a peaceful program to generate electricity.

"The suspension of enrichment is one step backward," Iranian foreign ministry spokesman Hamid Reza Asefi said. "Instead of setting preconditions that are both unreasonable and baseless, we should negotiate."

Diplomats say a compromise over enrichment will have to be found if the talks are to begin.

One diplomat close to the Vienna-based nuclear watchdog said it makes no sense to torpedo talks because of small-scale enrichment work Iran is already doing and which is not yet a proliferation risk.

"The United States will push very hard until the last minute in the hope of getting the Iranians to give in but at the end of the day they will accept some form of enrichment activity" in order to get talks started, said the diplomat, who requested anonymity.

The oft-repeated US position, however, is that not one centrifuge should be spinning as this could give Iran "break-out" knowledge to make nuclear weapons.

Among the compromises being considered are letting Iran use the centrifuge machines which enrich uranium, but empty of the uranium hexafluoride (UF6) feedstock gas that is refined into a more concentrated form of the isotope U-235.

It was to analyze this possibility that the US National Security Council asked ElBaradei for an assessment when he visited Washington just ahead of a meeting of six world powers in Vienna on June 1, a Western diplomat told AFP.

Britain, China, France, Germany, Russia and the United States defined their proposal at that meeting, which was then presented to Iran on June 6.

ElBaradei was asked three questions, according to the document:

-- "If centrifuges were left to spin in vacuum, i.e. without introduction of UF6, how much would be learnt."

-- "What R and D (research and development) could be linked to the fuel cycle but not involve enrichment and reprocesssing?"

-- What kind of inspection regime ("Protocol Plus") would we need to ensure effective verification in the country?"

A Western diplomat said the answer was that Iran could still learn much from even activities short of actually enriching uranium and that this "helped the United States, Britain and France argue persuasively in favor of full suspension as a precondition."

The IAEA said Iran could learn from spinning centrifuges empty such key information as the "life expectancy ... of key mechanical components" and data "needed for the development of more advanced centrifuge systems."

A second Western diplomat stressed that "the question that was posed to Elbaradei in Washington was merely a technical question and in no way indicated any change in position or any intention to change position" by the United States.

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