CHRONOLOGY: Iran's nuclear program

(Reuters) - Chief nuclear negotiator Ali Larijani, Iran's main contact with the West over Tehran's atomic program, has resigned, the government said on Saturday.

Here are the main events since it first emerged that Iran was carrying out sensitive work that it could use to make atomic bombs, although Tehran insists its activities are peaceful:

August 2002 - The exiled opposition National Council of Resistance of Iran reports the existence of uranium enrichment facility at Natanz and heavy water plant at Arak.

December 2002 - The United States accuses Iran of "across-the-board pursuit of weapons of mass destruction".

June 2003 - International Atomic Energy Agency (IAEA) report, after February inspection of Natanz and Arak, says Iran has failed to comply with nuclear Non-Proliferation Treaty.

October 2003 - Iran tells European Union negotiators France, Britain and Germany it will suspend all enrichment activities.

December 2003 - Iran signs protocol allowing snap inspections of nuclear facilities.

November 2004 - Iran promises EU negotiators it will suspend all nuclear fuel processing and reprocessing work.

September 2, 2005 - IAEA report confirms Iran has resumed uranium conversion at Isfahan. The European Union ends two years of talks in August after Iran said it would resume that work.

January 10, 2006 - Iran removes U.N. seals at Natanz enrichment plant and resumes nuclear fuel research.

February 4 - IAEA votes to report Iran to the U.N. Security Council. Iran ends snap U.N. nuclear inspections the next day.

February 14 - Iran restarts small-scale feeding of uranium gas into centrifuges at Natanz after 2-1/2-year suspension.

March 8 - IAEA report to Security Council says it cannot verify Iran's atomic activities are peaceful.

April 11 - Iran announces it has produced low-grade enriched uranium suitable for use in power stations; IAEA confirms.

June 5 - EU foreign policy chief Javier Solana delivers a package of incentives from world powers if Iran agrees to halt uranium enrichment.

July 31 - The U.N. Security Council demands that Iran suspend its nuclear activities by August 31.

August 22 - Iran responds to incentives offer saying it contains ideas that would allow for serious talks.

August 31 - IAEA announces Iran has not met deadline to suspend its atomic fuel program.

December 23 - Security Council votes for sanctions and gives 60 days to suspend enrichment. Iran calls the resolution illegal.

February 21 - A 60-day grace period to stop enrichment expires.

March 24 - The Security Council unanimously approves new arms and financial sanctions against Iran.

April 18 - IAEA says Iran has begun making nuclear fuel in its underground uranium enrichment plant.

May 23 - A confidential IAEA report says Iran has not suspended enrichment-related work, defying a second 60-day U.N. deadline.

Aug 21 - Iran and the IAEA say they agreed a timeline for answering outstanding questions about Iran's nuclear program.

Sept 25 - President Mahmoud Ahmadinejad says the issue of Iran's nuclear plans was "closed" and a matter to be handled by the U.N. watchdog.

Sept 28 - Six world powers agree to delay a vote on tougher U.N. sanctions on Iran until late November at the earliest, to wait for reports by the IAEA and Solana.

Oct 4 - Diplomats say Iran has installed close to 3,000 centrifuge machines, enough to start refining usable amounts of nuclear fuel if they worked without glitches.