Nuclear thaw: The deal between Iran and the big powers is of historic importance, but its risks must be carefully managed

Taken at face value, the deal between Iran and the major world powers to curb Tehran’s nuclear programme in return for an easing of sanctions is not merely to be welcomed. Just possibly the agreement – the culmination of a 12-year process – could signal the start of a thaw in relations between the West and, arguably, the Middle East’s biggest power, in the deep freeze since the Islamic revolution of 1979.

The protagonists in the accord are certainly of that opinion. “This deal offers an opportunity to move in a new direction,” said President Barack Obama, while Iran’s President Hassan Rouhani claimed that “a new chapter” had begun in his country’s relations with the world. But, as always with such grand bargains, the proof of the pudding will be in the eating.

Inevitably both sides have had to make concessions. Contrary to the wishes of American hardliners, the agreement does not place an indefinite straitjacket on Iran’s nuclear activities. “Every pathway to a [Iranian] nuclear weapon is cut off,” Mr Obama proclaimed – but only for 10 or 15 years.

Given the present chaos in the Middle East, even that temporary delay might seem a blessing. But much depends on just how intrusive and comprehensive the agreed international monitoring proves to be. Iran has a long track record of cheating. Even so the inspection regime, on paper, is among the toughest ever agreed to by a sovereign nation. Tehran has also had to accept that the United Nations arms embargo, contrary to its 11th-hour demands in Vienna, will remain in place.

None of this will satisfy critics, both within the US and abroad. Republicans – and even some Democrats – in Congress, as well as Israel and America’s traditional Sunni allies in the region like Saudi Arabia and Egypt, will not be shaken from their belief that an over-accommodating American President, in his anxiety to secure a foreign policy “legacy”, has been outmanoeuvred. The immediate challenge lies on Capitol Hill. The mathematics of presidential vetoes means that Republicans, despite their majority in the Senate – which has to approve the deal – will struggle to overturn it directly. But they can make life a misery for Mr Obama in other ways, such as by blocking presidential nominees. Nor should Israel’s influence on Capitol Hill be underestimated.

Simultaneously, the administration must embark on a diplomatic drive to convince its sceptical friends in the region that Mr Obama has not given away the store. This will be anything but easy. President Rouhani’s talk of a “new chapter” surely does not include an end to Iranian meddling in Yemen, Lebanon and Gaza, a brake on its ever-growing influence in Iraq, or withdrawal of support for the odious Assad regime in Damascus.

Indeed, the greatest short-term risk is that the deal will increase Tehran’s capacity to meddle, thanks to the release of billions of frozen dollars and the broader economic boost to Iran following the easing of sanctions. In that case, the nightmare of a generalised sectarian confrontation across the Middle East between Sunni and Shia Muslims could become a devastating reality. That, in turn, could lead fearful Saudis and Egyptians into the very regional nuclear arms race that these Vienna accords are supposed to prevent.

It is essential that the agreement is thoroughly scrutinised. The maxim of Ronald Reagan in his arms control negotiations with the Soviet Union, “trust but verify”, applies perfectly today. Nevertheless, many believed it impossible for a deal to ever be signed. The achievement is a large one, however closely its consequences must be watched.