The nuclear talks between Iran and P5+1 following the most stringent sanctions against Iran to date have opened new prospects for relaxation of tensions between Tehran and the West and for a U.S.-Iranian détente in the long run. The coming to power of new presidential administrations in both the United States and Iran, the additional sanctions, major geo-economic and geopolitical trends, and U.S.-Iranian economic and security cooperation imperatives all contributed to these dynamics. Some view the talks as a new beginning in U.S.-Iranian ties, which could herald the emergence of a U.S.-Iranian strategic relationship in the next 15 years. This work has developed three such possible strategic relationships: 1) strategic engagement involving a nuclear weapons-capable Iran; 2) comprehensive cooperation following a “Grand Bargain”; and, 3) incremental strategic engagement after a nuclear deal. These relationships deliberately focus on constructive engagement, skipping the status quo and a strike on Iran as two other possible outcomes. If they pull it off by 2030, a U.S.-Iranian détente would advance external integration of the region, aiding the U.S. strategy of fostering global connectivity. It would promote resolution of conflicts and development and reconstruction of countries ravaged by wars and sectarian violence. It would also enable Washington to deploy select military assets to other locales to address other challenges while repurposing remaining forces to face new threats in the Greater Middle East.