TIMELINE: Iran's nuclear program

(Reuters) - Six world powers agreed on Friday to push ahead with a third round of tougher sanctions against Iran unless reports later this month indicate Tehran has tried to address their concerns about its nuclear program.

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

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.

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.

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

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.