The report, circulated last week by agency head Mohamed ElBaradei to the International Atomic Energy Agency's board of governors, found that although Iran has made progress in revealing details about its past nuclear work, the agency's knowledge of Tehran's current atomic activities was actually diminishing.

Furthermore, Iran is continuing to defy UN demands that it suspend uranium enrichment.

The report's findings will be crucial for the UN Security Council in New York in deciding whether to improve a third, harsher round of sanctions against the Islamic Republic.

Here is a chronology of the international crisis over Iran's disputed atomic drive.

2002

-- August: Iranian exiles say that Tehran has built a uranium enrichment plant at Natanz, in the centre of the country, and a heavy water plant at Arak, southwest of Tehran, without informing the United Nations.

-- December: Satellite photos reveal the existence of nuclear sites at Natanz and Arak. The United States accuses Tehran of seeking weapons of mass destruction. Iran agrees to inspections by the International Atomic Energy Agency.

2003

-- February: IAEA chief Mohamed ElBaradei travels to Iran with a team of experts.

-- June: ElBaradei says Iran has not revealed the extent of its nuclear activities and urges Tehran to allow more thorough inspections.

-- August: A UN report reveals that traces of enriched uranium have been found in Natanz.

-- October: After meeting with Britain, France and Germany, Iran agrees to suspend uranium enrichment, a process used to make both nuclear fuel as well as nuclear bombs, and sign the additional protocol to the Nuclear Non-proliferation Treaty, formalising tougher inspections of nuclear facilities by the IAEA. No evidence is found that Iran has ceased enrichment.

-- November: An IAEA report says there is no proof that Iran is pursuing nuclear weapons, but that conclusion is disputed by the United States.

-- December: Iran signs the additional protocol.

2004

-- June: IAEA complains that Iran is not providing "full, timely and pro-active" cooperation with inspectors.

-- November: Iran agrees to suspend uranium enrichment and reprocessing activities while talks with the so-called EU-3, made up of Britain, France and Germany, on trade and economic issues are underway.

2005

-- August: Mahmoud Ahmadinejad is installed as Iranian president. Iran recommences uranium conversion activities at its nuclear facility in Isfahan. The EU breaks off negotiations.

-- September: The IAEA finds Iran in violation of the NPT and passes a resolution reserving the right to send Iran's case to the Security Council.

2006

-- January: Iran breaks IAEA seals at its Natanz nuclear research facility.

-- February: the IAEA votes to report Iran to the UN Security Council. Iran resumes uranium enrichment at Natanz.

-- March: IAEA says it cannot verify that Iran's nuclear activities are peaceful.

-- July: UN Security Council demands Iran halt work on nuclear fuel, threatening sanctions for the first time.

-- August: IAEA says Iran has failed to suspend the programme.

-- December: UN Security Council votes to impose sanctions on Iran's trade in sensitive nuclear materials and technology. Iran condemns the resolution and vows to press ahead with enrichment.

2007

-- January: Iran says it has blocked entry to 38 IAEA inspectors in retaliation to sanctions.

-- February: IAEA says Iran failed to meet a deadline to suspend uranium enrichment and has actually expanded its work.

-- March: UN Security Council adopts further sanctions, while offering more incentives to end the nuclear stand-off.

-- April: President Ahmadinejad says Iran can produce nuclear fuel on an industrial scale.

-- October: Ali Larijani resigns as top Iranian negotiator and is replaced by Deputy Foreign Minister Said Jalili, considered to be more hardline. US President George W. Bush warns of a possible World War III if Iran is allowed to develop nuclear weapons.

-- November: the IAEA finds in a new report that while Iran has been telling the truth about key aspects of its past nuclear activities, its knowledge of Tehran's current nuclear activities is diminishing. The report also finds that Iran is continuing to defy UN demands to suspend enrichment.

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