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What would a deal look like? The United States has long demanded that Iran stop all enrichment of uranium, a process that allows it to produce the fuel necessary for an atomic bomb. Iran has insisted it has the right to enrich for a peaceful nuclear program. Now, it seems a smart compromise might be reached. Washington has signaled that it will ask Iran to stop enriching uranium to 20 percent, the level from which fuel can be easily converted for military purposes. Iran has indicated that it might be willing to accept such a limit and would enrich up to only 3.5 or 5 percent. Then Iran could claim that it has preserved its right to enrichment.

Iran would still have a stockpile of uranium enriched to 20 percent, produced over the past two years, perhaps enough to make a nuclear bomb. Tehran has rejected Washington’s demands that this uranium be shipped abroad for safekeeping, saying it is needed for the production of medical isotopes. But Iran almost accepted a deal on this point in 2009 and proposed one in 2010 in which it would have shipped out low-enriched uranium. Statements from officials on both sides suggest that they might embrace elements of those proposals, which involved shipping away some of Iran’s uranium stockpile in return for completed fuel plates that are used in the process of making medical isotopes.
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The crucial point on which Iran should make deep concessions is comprehensive inspections. The 2011 International Atomic Energy Agency report lays out a series of indicators that Iran is pursuing a weapons program. The P5+1 should use that as a checklist of activities that Iran would commit to refraining from and insist that Iran allow the IAEA unfettered access to its sites until the agency is satisfied that any such military program has been shut down. Iran would have to receive some reward for accepting such unprecedented inspections, and the obvious option would be the relaxation of sanctions, step by step, as inspections proceed unimpeded.

For any deal to stick, it has to be accepted by two groups. There are reasons to think Iran’s hard-liners, led by Supreme Leader Ayatollah Ali Khamenei, might be amenable. Khamenei has consolidated power: He has beaten back the Green movement; accommodated one key rival, Ali Akbar Hashemi Rafsanjani; and sidelined another, President Mahmoud Ahmadinejad. Khamenei has also given himself room to make concessions on the nuclear program.
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• http://www.washingtonpost.com/opinions/iran-nuclear-negotiations-can-result-in-a-robust-deal/2012/04/11/gIQAAmaQBT_story.html