A draft deal to start defusing nuclear tension between Iran and big powers has foundered in rows over details and goals, reflecting mistrust and an Iranian tendency to play for time. The breakdown of a draft plan for Iran to part with stocks of potential nuclear bomb material in exchange for fuel to run a nuclear medicine site has prevented follow-up talks on a broader solution to Iran's contested nuclear program. u How did the plan originate? Iran is running out of specially fabricated fuel imported in 1993 to run a Tehran research reactor that produces radioactive isotopes for cancer treatment. The seeds of a deal were planted when world powers saw an opportunity to reduce the risk of Iran using its enriched uranium stockpile to develop atomic bombs. In talks with six world powers in Geneva on Oct. 1, Iran agreed in principle to send the bulk of its low-enriched uranium (LEU) to Russia and France for further processing and conversion into fuel plates for the Tehran reactor, Western officials said. u Has the fuel plan advanced towards fruition? No. Iran balked at finalizing details at Oct. 19-21 talks in Vienna with the other parties presided over by Mohamed ElBaradei, head of the International Atomic Energy Agency (IAEA). To knock heads together, he drafted a plan prescribing that Iran send out 75 percent of its LEU stocks by the end of this year and get it back as fuel for the medical reactor before its reserve peters out about a year from now. The United States, which would upgrade the reactor's safety gear and instrumentation under the deal, and France and Russia swiftly endorsed ElBaradei's draft. Iran called for amendments and more talks, but left unclear what its bottom line was. u What does Iran want? Iranian officials say Tehran prefers to obtain the fuel from foreign producers, or swap domestic LEU simultaneously for imported material. Some publicly oppose parting with any LEU, calling it a vital strategic asset against Iran's enemies, referring to the United States and Israel. Others demand full delivery of reactor fuel before any LEU leaves, and insist it could go only in small, phased amounts, without a deadline. u Could the powers take up Iran's suggestions? Highly unlikely. Western powers see Iran stalling to prevent any reduction in its LEU reserve, the very appeal of the plan to them, since Tehran has accumulated enough of the material to make one bomb if it were enriched to high purity. It will have enough for two by early next year, proliferation analysts say. US Secretary of State Hillary Clinton has said the plan will not be renegotiated and urged Iran to accept it to inspire confidence in its professed intention to use enriched uranium only for the peaceful production of electricity. u How did the promise of Geneva fade? Western diplomats fear Iran made only a show of flexibility in Geneva to prevent six-power unity over the need for tougher UN sanctions against Tehran, with Russia and China, major trade allies of the Republic, remaining opposed. Iran keeps both on side by seeking more talks it hopes will push back Western red lines again -- aware that Washington once rejected negotiations before Iran halted enrichment, but now wants a deal over how Tehran uses its enriched uranium. u What is being done to save the plan? ElBaradei said he was considering face-saving compromises. These could include Iran putting LEU into an escrow account under IAEA supervision in a friendly third country, such as Turkey, until reactor fuel arrives. Iranian media quoted a senior official on Saturday as rejecting that idea. ElBaradei said last week the main stumbling block to agreement was how to sequence deliveries in each direction. A bigger barrier may be Iran's convoluted power structure. It militates against decisions to shift strategic direction, while dominant hardliners believe any negotiated rapprochement with Western powers can only undermine the Revolution. u Is there fallout from the impasse? Yes. It has led to the indefinite postponement of a second, more ambitious Geneva round, originally set for the end of October, where the powers aimed to coax Iran into curbing enrichment activity as a whole in exchange for sanctions relief and trade benefits. Moreover, in holding up the fuel plan, Iran has stymied US President Barack Obama's policy of engagement to settle the nuclear dispute. Barring a breakthrough by the end of the year, the United States, France, Britain and Germany will pursue painful sanctions against Iran's huge oil sector.