Diplomatic sources in Vienna said they expect the IAEA report to be released on Wednesday afternoon or on Thursday.

It will be the first of two crucial reports -- a second by the EU's foreign policy chief Javier Solana is set to be released later this month -- that could persuade the UN Security Council in New York to impose new sanctions against Iran if the findings of the report are negative.

The UN has already slapped two rounds of sanctions against Iran over its controversial nuclear drive.

And the United States and some of its European allies are backing a vote for a third round if the reports by Solana and International Atomic Energy Agency chief Mohamed ElBaradei show that Iran is continuing to obfuscate on the true nature and extent of its nuclear activities.

Washington, in particular, believes Tehran is seeking the atomic bomb and has not ruled out the option of military action to end its defiance.

Iran, for its part, insists it wants only to generate electricity for a growing population.

Not surprisingly, the stakes have been raised during the run-up to the release of the IAEA report.

On Monday, British Prime Minister Gordon Brown described the Islamic republic as "the greatest immediate threat to non-proliferation" and vowed Britain would lead the way in pushing for tougher sanctions against Tehran, both at a UN and EU level.

French President Nicolas Sarkozy and German Chancellor Angela Merkel also said additional sanctions could be the answer and raised the possibility of reducing their countries' trade ties with Tehran.

Israel, which sees its very existence under threat from Iran's nuclear ambitions, has been even more outspoken, saying that "all options are on the table", including the use of military force.

And Israeli Deputy Prime Minister Shaul Mofaz called for ElBaradei to be removed as head of the IAEA, saying the Egytian-born diplomat had turned a blind eye to Iran's atomic drive.

At the same time, more conciliatory tones have been heard from China, which together with Russia, also holds a permanent seat on the UN Security Council alongside the western powers of the US, Britain and France.

China believes that "sanctions, particular unilateral sanctions, will do no good," a foreign ministry spokesman said on Tuesday, even as Beijing urged Iran "to respond to the concerns of the international community and take a more flexible stance so as to promote a resolution on the issue."

Iran is adamant that it has answered all of the IAEA's outstanding questions and Iranian officials insisted on November 1 that both sides were satisfied with the outcome of a series of visits by the agency's deputy director general Olli Heinonen and a delegation of its technical experts.

But diplomats in Vienna said that western officials remain sceptical that after long years of dissumulation, Tehran has finally opted for full and complete disclosure of both past and present nuclear activities.

Furthermore, Iran is refusing outright to bow to UN demands that it halt uranium enrichment, which can be used to produce reactor fuel or, in highly refined form, atom bomb material.

On Tuesday, a diplomat in Vienna said that Iran recently rejected an approach by IAEA chief ElBaradei for a meeting ahead of the report's publication.

ElBaradei had proposed going to Iran, with some suggestions that he might even meet Iranian Supreme Leader Ayatollah Ali Khamenei.

"But they (the Iranians) felt that the time was not right, so the meeting was postponed," the diplomat said on condition of anonymity.

Nevertheless, Tehran promptly rejected the charge.

"Mr ElBaradei's trip is on the agenda and its definite date will be decided when the two sides agree," foreign ministry spokesman Mohammad Ali Hosseini told Iranian state media.

And Iran's ambassador to the IAEA, Ali Asghar Soltanieh, said: "Currently, we are in the process of defining a situation for this meeting and his visit to Iran. The invitation for Mr ElBaradei is still on."

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