In the aftermath of the summit meeting in Kazakhstan between Iran and the great powers, there is an unusual sense of optimism in the relevant capitals.
While in the past Iran's media and politicians greeted such meetings with denunciation and pledges of defiance, this time the regime's official class sounds moderate in tone and tempered in its claims. Even jaded American officials accustomed to Iranian obstinacy appear somewhat sanguine.
After nearly a decade of diplomacy, there is a faint and perhaps fleeting light at the end of one of the world's most durable tunnels. The challenge for the next round of talks, in April, is to cement the progress that has been made and finally transact a resilient arms control agreement.
The essential aspect of Western strategy is that nuclear concessions by Iran will be met by relaxation of economic penalties. In diplomatic parlance this is known as "more for more" — the more of its nuclear portfolio Iran concedes, the more financial benefits it will reap.
Indeed, the sanctions regime orchestrated by the Obama administration has succeeded beyond the imagination of its skeptics and has managed to largely segregate Iran from the global economy.
But a conclusive resolution of the prevailing impasse is unlikely to be achieved through an exchange of nuclear concessions for sanctions relief. For the great powers to continue to make progress on this issue, they need to consider not just Iran's economic distress but also its security predicament.