Ray Takeyh of the Council on Foreign Relations suggests that unrealistic demands made by Iranian negotiators may be sinking any hope of a compromise on the nuclear issue:
It is traditional Iranian statecraft to give little and hope to get a lot. So Iranians came into these negotiations with some rather extraordinary demands, particularly [that] their right to uranium enrichment be officially recognized--which is impossible, given the fact that the enrichment stands in violation of Security Council resolutions and the International Atomic Energy Agency's ( IAEA) board of governor's injunctions. The United States and the other powers just could not get the Iranians to abandon that demand and their demand for substantial sanctions relief in exchange for discussing the disposition of their uranium enriched to 20 percent.
And Takeyh provides a useful reminder that Iran's intransigence on this issue dates back to 2006:
The United Nations' six Security Council resolutions have asked Iran to suspend all enrichment and reprocessing activities, have asked Iran to come to terms with the IAEA regarding previous or ongoing weaponization activities, and to clarify all ambiguities regarding its nuclear program. At this point, Iran has not discharged those obligations, [which] go back to 2006. So for some six years, Iran has rebuffed those demands from the international community. In these particular talks that have just taken place, the talks focused more specifically on this 20 percent enrichment. The world powers asked Iran to stop producing 20 percent enriched uranium [which can more easily be converted to weapons grade uranium], to ship out the existing supplies of 20 percent enriched uranium, and to shut down the Fordow underground facility, which is being used to enrich uranium to the 20 percent level. Iran rejected those requests.
So far, the negotiations seems to be going according to a certain plan: Call it "Delay and Enrich." The Iranians haven't stopped enriching uranium during these months of negotiations. It would be fair to say, in fact, that the negotiations represent a crucial component of their enrichment strategy.