THE interim deal concluded on November 24th between six world powers and Iran is much better than its many critics allow. In return for six months of “limited, temporary…and reversible” relief from some international sanctions, Iran has said it will not just freeze its progress towards a possible nuclear bomb, but actually take a few steps back. This, too, is limited, temporary and reversible; nothing is being decommissioned, and six months is a short time. But if further negotiations can cement the gains in place, they would mark a turning point in efforts to stop nuclear proliferation—and perhaps in regional politics more broadly (see article).

The agreement was brought about by a multilateral process in Geneva and secret parallel discussions between the Obama administration and Iran which began in August, when Iran’s new president, Hassan Rohani, took office. Both sets of negotiations were conducted in an atmosphere of constructive endeavour, a far cry from the sterile declarations and mutual suspicion of the past.

A nuclear-weapons programme needs either uranium which has been highly enriched—something achieved by passing the stuff repeatedly through cascades of whirling centrifuges—or plutonium. At present the International Atomic Energy Agency (IAEA) reckons that Iran has almost 200kg of 20%-enriched uranium in a form that could easily be enriched up to the 90% or so needed for a bomb. Under the terms of the deal (see table on next page) Iran will get rid of this stock, either by putting it in a form that is hard to enrich further or by mixing it with unenriched uranium, thus diluting it to less than 5%. At the same time it will freeze its enrichment capabilities at their current capacity, undertake no further enrichment beyond the 5% level, and do nothing to increase the 7,200kg stockpile of low-enriched uranium that is currently in a form that can easily be further enriched.

Speed bumps for breakouts

Mark Fitzpatrick of the International Institute for Strategic Studies, a think-tank in London, believes that the effect of the deal is to double the “breakout time” it would take Iran to produce enough material for a few nuclear weapons. Before the deal this was estimated at perhaps six weeks, and was steadily shortening.

The deal addresses the other possible route to the bomb by stopping most work on a reactor at Arak which was to have been ready for commissioning late next year. The Arak reactor is of a design particularly well suited to producing plutonium, and needs no enriched uranium in order to do so. Once the reactor is fuelled up, any attack on it would release a plume of radioactivity; this makes its commissioning something of a point of no return as far as military action against Iran is concerned. The deal also stops all work on facilities that might be used to extract plutonium from its spent fuel. These constraints are in large measure thanks to the French, whose objections to insufficient action on Arak prevented an agreement from being reached two weeks earlier.

Iran has also said it will co-operate with a far more intrusive inspection regime; this makes the deal very different from the one reached with North Korea in 2005, which the Koreans then broke. Iran has promised to answer all the questions posed by the IAEA about what the agency refers to as the “possible military dimensions” of its nuclear programme. It will provide access to nuclear sites hitherto off-limits, possibly including the Parchin military base where Western intelligence agencies think it tested a detonation system for a bomb.

In return for taking these steps, Iran gets access to about $4.2 billion held in currently frozen bank accounts and some easing of restrictions on trade in petrochemical products, precious metals and parts for aircraft and cars, a package thought to be worth $7 billion to its economy over the six months. Sanctions on oil which will cost Iran $30 billion over the same period remain firmly in place, providing a lot of leverage as negotiators start work on a final deal. Critics, though, argue that the psychological impact of relaxing these lesser sanctions will weaken the greater ones, particularly when it comes to some countries that have only toed the line with reluctance.

A stronger criticism is that the deal says nothing about Iran’s “right” to enrich uranium, which the country sees as “inalienable”. The Nuclear Non-Proliferation Treaty (NPT) gives signatories such as Iran a right to the benefits of peaceful nuclear energy. That can be construed as a right to enrich if the enrichment is for peaceful purposes, though other interpretations are available. Given that Russia, which built Iran’s only large reactor, at Bushehr, has a ten-year contract both to provide its fuel and to remove its waste, it is very hard to see Iran’s large and growing enrichment programme as entirely for peaceful purposes; the country’s record of cheating when it comes to inspections makes it hard to trust. Yet the deal implicitly recognises that Iran will stay in the enrichment game.

Not there yet

But those insisting that Iran must forswear any enrichment in the future are demanding something that almost certainly cannot be negotiated. Whatever the pressure of sanctions, Iran will not consent to an agreement it regards as a national humiliation. Given the promise of the interim deal, ratcheting up sanctions now, as some in America’s Congress urge, is more likely to weaken international support for America’s position—and for the existing sanctions—than to draw concessions Iran would never otherwise make.

The objective of the negotiations’ next stage will not be to make it impossible for Iran ever to acquire nuclear weapons. Instead, its aim should be to make it unfeasibly difficult for Iran to get a bomb by stealth and to stretch the period it would need for a nuclear breakout to a year or so, thus giving time to mount a response.

David Albright, a former weapons inspector and founder of the Institute for Science and International Security, a think-tank in Washington, DC, says a final deal will have to require Iran to abandon the Arak reactor—perhaps replacing it with one of a different design that has safeguards built in—and close its Fordow enrichment site, which is buried deep beneath a mountain and thus very hard to bomb. Iran would also have to adhere to the Additional Protocol of the NPT, giving IAEA inspectors enhanced rights of access to ensure that it is not cheating.

There is room for manoeuvre on the number and quality of the centrifuges that Iran could retain at Natanz (its other main enrichment site) the size of its low-enriched-uranium stockpile, and an Arak replacement. Also unanswered is the question of how quickly sanctions relief should be granted in return, and how long the agreement should last. American negotiators would be unhappy with anything less than about ten years. They think it will take that long for a culture of compliance and transparency to build up.

Getting a long-term deal that meets all those requirements will not be easy. Iranian negotiators may well be under pressure from factions at home to get tougher. Mr Rohani continues to enjoy the backing of the supreme leader, Ayatollah Ali Khamenei, who has the final say in all matters of state. But conservatives, including the ubiquitous and powerful Revolutionary Guard, will not just be loth to accept a plan that would stymie their ambition to acquire a nuclear bomb, as any final comprehensive deal must seek to do. They will also hate the idea of any deal that seems to point towards a “normalisation” of relations with America and the West.

Mr Rohani has been careful, so far, to give no hint that he would dilute the theocratic essence of the regime. Some of Iran’s conservatives, though, fear that he could become an Iranian Gorbachev, a man whose attempts to reform the system and make peace with a long-standing enemy could lead to its downfall.

The Revolutionary Guard could, by obstructing the inspections the deal requires, do a lot to derail a more durable follow-up agreement. And the approach taken in the next stage of the negotiations could be less constructive than what has been seen so far. But enough has already been agreed to suggest that success is possible.