Whether the interim agreement between Iran and its Western interlocutors lasts the full six months, and what might follow when that period ends, will depend less on the evidence of compliance (from both sides) than on whether, when the initial deadline approaches, all realistic alternatives open to the US and its allies are worse than continuing with something akin to the new framework.

Underpinning that calculus, and indeed at the heart of any resolution of the nuclear question, lies a wider set of strategic considerations in Washington and Tehran. If those concerns can be reconciled, they will shape the regional outlook for decades to come.

The strategic logic of the present situation is simple: the status quo in the Gulf region serves the interests of the US and Iran less well than movement towards a pragmatic accommodation on the nuclear issue.

The real test, however, is whether both sides would also prefer to move towards more credible and predictable mutual dealing that encompasses — but goes well beyond — the specific matter of nuclear proliferation. Logic strongly suggests the US would take that approach, and seek reassurance in regard to the strategic behaviour and intent of Tehran, despite the political reservations that have been raised in Jerusalem and Riyadh.

The reasons for that inclination are as irreversible as they are straightforward.

US priorities are being reshaped by domestic economic and social pressures that foster popular aversion to engagement in intractable regional conflicts. There is growing acceptance of the limits to the possible in foreign policy, not least because of the profound resistance of Middle Eastern friends and foes alike to US advice, let alone tutelage, even where US interests are directly engaged.

Strategic horizons are also changing. US energy security concerns are abating, Israel is far more secure than any of its neighbours, and with shifting US political demographics and recognition that US interests in the Indo-Pacific in coming decades will have greater importance than its interests in the Middle East, the case for renewed US military intervention in the region is unlikely to outweigh the arguments for scaling back US foreign policy ambition in the Gulf.

On the Iranian side, the regime has every reason for increased confidence so far as its strategic outlook is concerned.

It gambled, and won, when it decided to consolidate the Assad regime's hold on power in Syria. It has witnessed in Syria the West's unwillingness to countenance military conflict in support of imprecise and unrealistic political objectives. The US-Russia deal on Syrian chemical weapons did not disadvantage Iranian interests, nor has its influence in Iraq and Lebanon diminished.

At the domestic political level, President Rouhani has played his cards well. The intellectual acumen and experience of those responsible for arguing the case for engagement is impressive. The interim deal has been presented as an affirmation of Iran's sovereign right to enrich uranium. Rohani continues to have the backing of Supreme Leader Khamenei. And arriving at a deal which could be criticised at home for its limited rewards for compliance and for its overall intrusiveness is less problematic than failing to address the popular support for change (evidenced by his election victory) and an easing of the burden of sanctions.

The larger question, however, is where, over time, the balance of advantage rests between the US and Iran in the overall management of regional security. Among the various factors likely to shape the answers to those questions in coming months, two stand out.

The first is whether the Iranians under Rouhani succeed in establishing their political dominance over their conservative critics to such a degree that the latter are marginalised or limited to a spoiling role in Iran's external activities.

Rouhani has assembled a formidable team to advise him on the political and diplomatic challenges ahead. But the results will depend, ultimately, on Iranian economic performance (strengthening sanctions on Iran would overwhelmingly be to the advantage of those who least wish Rouhani and his supporters to succeed). 

The second factor is whether the US and Iran can develop a degree of mutual understanding about their respective security interests that would permit the US to accept the possibility of Iran remaining a nuclear threshold state for the foreseeable future and that would allow Iran to accept America's continuing regional role and presence.

Arriving at such an understanding is possible. Whether a solution to the proliferation issue can be found will probably depend on it.

Photo by Flickr user European External Action Service.