FACTBOX: Key moments in Iran nuclear diplomacy

(Reuters) - Six world powers held talks with Iran near Geneva on Thursday on how to end a long-running standoff over Iran's nuclear program, which Tehran says is designed purely for generating electricity.

Western officials say that if Iran does not show a willingness to compromise on the program, which the West fears is aimed at producing weapons, they will push for a fourth round of sanctions against Tehran.

Following are key moments in negotiations with Iran on its nuclear program:

IRAN-EU3 TALKS

October 2003 - After the U.N. nuclear watchdog says Iran hid its nuclear enrichment program from U.N. inspectors for nearly two decades, Iran agrees to negotiate with Britain, France and Germany on a package of economic and political incentives and promises to suspend its uranium enrichment program. European officials involved in the "EU3" talks with Iran say they are aimed at reaching a peaceful agreement with the Iranians that would avoid military action.

U.S. officials are skeptical and say that the talks are doomed to fail. The vast majority of members of the governing board of the U.N. nuclear watchdog in Vienna, the International Atomic Energy (IAEA), agree not to refer Iran's nuclear program to the U.N. Security Council for possible sanctions while negotiations between Tehran and the EU3 are underway.

SECURITY COUNCIL REFERRAL

February 2006 - After 2-1/2 years of fitful talks, the European trio break off their negotiations with Iran in January 2006. The following month Iran begins enriching uranium and the IAEA board of governors votes to refer Iran's nuclear program to the U.N. Security Council.

IAEA chief Mohamed ElBaradei makes clear that he opposes sending the Iran issue to the Security Council, and IAEA officials say it is because ElBaradei fears the situation could escalate out of control and lead to military strikes against the Islamic Republic.

P5+1 OFFERS

June 2006 - The United States, Russia and China join forces with the EU3 and decide to make a new offer to Iran. European Union foreign policy chief Javier Solana presents the Iranian government with an offer on behalf of the six powers. The group, referred to as the P5-plus-1 -- five permanent Security Council members and Germany -- or the EU3+3, make clear that they will hold off on any Security Council action if Tehran halts enrichment work and agrees to negotiate with them.

The United States, which severed relations with Tehran in 1980, agrees to provide incentives as part of the package on offer to Iran as well, including civilian aircraft parts and information technology. Iran does not accept the offer.

June 2008 - The six powers agree to beef up their proposal. Iran has yet to respond to the renewed offer.

SECURITY COUNCIL RESOLUTIONS AND SANCTIONS

July 2006 - The Security Council orders Iran in a legally binding resolution to halt its nuclear enrichment program and other sensitive activities.

December 2006 - The Security Council passes a new resolution imposing travel restrictions and asset freezes on Iranian firms and individuals linked to Iran's nuclear and missile programs for refusing to suspend enrichment work. The resolution also bans the export of equipment that could be used in Tehran's missile and nuclear programs.