The rapid pace of events since Iranian President Hassan Rouhani took office this past summer has significantly increased the possibility of a successful negotiation on Iran's nuclear program, thereby forestalling either a military strike on Iran or the emergence of a nuclear-armed or nuclear-weapon-capable Iran. Either of these latter eventualities would unleash unknown but likely very serious consequences on an already stressed international situation. The United States thus should vigorously engage, with Iran and with our allies and partners, accepting risks when necessary, to achieve a diplomatic breakthrough that would meet President Obama's criteria of being meaningful, transparent, and verifiable.

The technical outlines of any such agreement have been sketched out many times, by the P5+1 in its September 2009 offer to Iran and in studies and essays by many analysts, myself included. Iran will have to largely forgo use of its huge enrichment infrastructure, including closing the Fordow site, stop work on the Arak heavy water reactor, agree to much more intrusive IAEA inspections and implementation of a safeguards agreement, and come clean on its nuclear-related military research. Iran will insist on enrichment as a principle, but that would have to be limited in quantity and quality -- that is, no more than 5 percent, with all but immediately required enriched uranium stored "temporarily" outside Iran and the whole process vigorously monitored. The P5+1 will have to lift or suspend nonmilitary sanctions, especially those targeting hydrocarbons trade and banking not tied to illicit nuclear materials trade, and de facto will have to countenance a minimal amount of Iranian enrichment.