December 11: Opposition coalition NCRI says that Iran's programme was shut down in 2003 and re-started a year later, adding that the recent US analysis was misleading.
March 3: UN Security Council adopts third sanctions resolution targeted at Iran's nuclear programme.
May 14: Russia's foreign minister says an offer to negotiate and security guarantees for Iran could be given by the group of six. The US administration denies that security guarantees were being considered.
May 26: The IAEA says Iran's alleged research into nuclear warheads is a matter of serious concern and asks for more information on Tehran's missile-related activities.
June 1: In reaction to the IAEA's report, Tehran says it might have to limit cooperation with them.
June 14: Solana, in Tehran, presents Iran with an offer from world powers with economic and other benefits. However, Iran rejects any suspension of activities.
July 10: Iran tests nine missiles in the Gulf.
July 19: Iranian officials rule out freeze in uranium enrichment during talks in Geneva, attended for the first time by a senior US diplomat.
August 2: An informal deadline lapses for Iran to respond to an offer from the United States, Britain, France, Germany, China and Russia for talks.
September 15: The IAEA says Iran blocks a UN inquiry into whether it researched ways to develop a nuclear bomb.
February 5: Russia says it plans to start up a nuclear reactor at the Bushehr plant by the end of 2009.
February 19: An IAEA report shows a significant increase in Iran's stockpile of low-enriched uranium; enough, physicists say, for conversion into highly enriched uranium for one bomb.
|Obama makes a statement on Iran with Sarkozy, left, and Brown at the G20 summit in Pittsburgh [AFP]
March 20: Barack Obama, as the new US president, calls for "engagement that is honest and grounded in mutual respect" with Iran.
Iran cautiously welcomes the overture, but said it wanted to see "practical steps".
April 9: Ahmadinejad says Iran has mastered the nuclear fuel cycle and also tested further advanced machines for enriching uranium. President also inaugurates the nation's first atomic fuel fabrication plant near Isfahan.
June 5: A quarterly IAEA report says Iran now has 7,231 centrifuge enrichment machines installed, a 25 per cent increase in potential capacity since March.
June 12: Ahmadinejad re-elected president. Protests break out by moderates who say the result was fixed.
August 21: Iran allows IAEA officials to inspect the Arak heavy-water site as well as an upgrade to IAEA monitoring at the Natanz uranium enrichment plant. Diplomats say there has been no increase in the number of centrifuges enriching uranium since the end of May.
August 28: The IAEA reports Iran has slightly reduced the scale of its uranium enrichment. But it has also raised the number of installed centrifuge machines by some 1,000 to 8,308.
September 7: Ahmadinejad says Iran will continue its disputed nuclear work and will never negotiate on its "obvious" rights.
September 9: Iran hands over a package of proposals to six world powers - the US, Russia, China, France, Britain and Germany - which it says addresses "various global issues" and represents a "new opportunity for talks and cooperation".
September 17: Ahmadinejad says Iran would "never" abandon its nuclear programme to appease Western critics.
September 25: The IAEA says Iran has told it about a second uranium enrichment plant under construction. Obama announces that the US, UK and France provided evidence to the IAEA showing Iran has been developing a covert uranium enrichment facility near Qom for several years.
September 26: Ahmadinejad reacts strongly to international condemnation of the second uranium enrichment facility, saying it was within the "parameters of the UN nuclear watchdog's rules".
September 27: Hillary Clinton, the US secretary of state, welcomes Iran's decision to allow IAEA inspectors into a newly disclosed uranium enrichment plant.
September 29: Iran test-fires several ballistic missiles.
September 30: Iran says it will not negotiate over its right to develop a nuclear programme when it meets officials from the five permanent members of the UN Security Council and Germany in Geneva on October 1.
October 1: Iran meets six world powers in Geneva. Saeed Jalili, Iran's chief nuclear negotiator, holds talks with William Burns, a senior US official in Geneva, in the most high-level US-Iranian contact in three decades.
October 3: The New York Times reports that staff at the International Atomic Energy Agency have written a confidential analysis conveying that Iran has "sufficient information to be able to design and produce a workable" atom bomb.
October 4: The IAEA announces that its inspectors will examine the Qom plant plant on October 25.
October 21: The IAEA says Iran has agreed to consider a deal which could see it ship out most of its enriched uranium to Russia.
October 23: Iran fails to meet the deadline to accept the IAEA deal.
November 17: Iran rules out sending its enriched uranium abroad for further processing, saying it would prefer to purchase the required fuel from other countries and keep its low-enriched uranium.
November 29: Iran responds to an IAEA resolution demanding that it halt the construction of a newly revealed enrichment facility near the city of Qom by announcing that it will build 10 new nuclear plants.
December 2: The IAEA passes a resolution criticising Tehran for defying a UN Security Council ban on uranium enrichment and rebukes it for secretly building a uranium enrichment facility near the city of Qom. Ahmadinejad rejects the resolution as "illegal".
December 11: The US, Britain and France warn Iran that it risks more sanctions unless it immediately complies with a series of UN Security Council resolutions regarding its nuclear programme.
December 12: The US dismiss an Iranian offer to exchange nuclear fuel, saying it was inconsistent with a deal that would allow Iran to avoid further sanctions.
January 3: The United States calls for fresh sanctions against Iran at the UN Security Council following expiry of year-end deadline to respond to Washington's offer of economic and diplomatic concessions.
January 21: Iranian and Russian officials announce that Iran's first nuclear power plant built with Russian help will be operational by the middle of this year.
January 27: UK-based International Institute for Strategic Studies predicts Iran will have enough low-enriched uranium for a nuclear bomb by end of the year.
February 2: Ahmadinejad gives a speech on state television, saying that Iran would have "no problem" with sending out its stocks of low-enriched uranium under a deal with Western powers.
February 7: In a speech at an exhibition on laser technology, Ahmadinejad tells Ali Akbar Salehi, the head of Iran's nuclear programme, to begin enriching uranium.