The “first step agreement” between Iran and the P5+1 is the most dramatic evidence of the Barack Obama administration’s newfound commitment to recasting alliances and security structures throughout the Middle East. For the first time in a generation, US policy in the broader Middle East has begun to build diplomatic, consensual frameworks for the future that are aimed at reducing, rather than promoting, regional instability and undermining states and their institutions.

Iran is currently front and center in this regard, but the surprisingly efficient destruction of Syria’s chemical weapons arsenal should also be counted among the policy's first notable achievements. As Obama himself said on Nov. 23, after the Iranian agreement was reached, “Diplomacy [has] opened up a new path toward a world that is more secure — a future in which we can verify that Iran’s nuclear program is peaceful and that it cannot build a nuclear weapon.” This development is a welcome, if much-belated, turnabout and counts as the best news in many years.

The potential for a far broader regional detente, built upon closing the nuclear file, offers opportunities to reshape relationships throughout the region and beyond. For more than a generation, Iran has been ground zero of the demonized “axis of evil.” As such, it was impossible for Washington and its allies to consider it a legitimate partner for productive diplomacy, let alone regional cooperation. That stalemate, so destructive for peoples throughout the region, is now thawing.

Iran’s power throughout the region as the political and ideological lodestar of the “axis of resistance” continues to obstruct the regional policies of the United States and its allies in Syria, the Gulf and elsewhere. But the changes now under way will establish a new and challenging context for old relationships involving not only those alliances associated with Tehran but also those associated with Washington.