TIMELINE: Iran's nuclear program

(Reuters) - Iran welcomed a U.S. report on Tuesday contradicting assertions by the Bush administration that Tehran was intent on building an atomic bomb, and the Islamic Republic said it was becoming clear its plans were peaceful.

Here is a chronology since it emerged that Iran was carrying out sensitive work that it could use to make atomic bombs.

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 - An IAEA report, after February inspection of Natanz and Arak, says Iran has failed to comply with nuclear Non-Proliferation Treaty.

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.

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.

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.

August 31 - IAEA announces Iran has not met a 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.

March 24, 2007 - The Security Council unanimously approves further 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.

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

Oct 20 - Saeed Jalili is named to replace chief nuclear negotiator Ali Larijani, who resigned.

Oct 24 - The U.S. imposes new sanctions on Iran and accuses Revolutionary Guard of spreading weapons of mass destruction.

Nov 2 - Britain, France, Germany, the U.S., Russia and China agree to push ahead with a third round of tougher sanctions.

Nov 15 - IAEA says Iran has made important strides towards transparency but it remains unable to ascertain Iran does not have a secret, parallel military enrichment program.

Nov 30 - The EU expresses disappointment with Iran after more talks with its main nuclear negotiator in London. World powers meeting in Paris the next day fail to decide on further sanctions.

Dec 3 - A U.S. National Intelligence Estimate says Iran had put its bid to build a nuclear bomb on hold in 2003 and it remains on hold. Iran welcomes the report the next day.