George W Bush has huffed and puffed about using force to thwart Iran’s nuclear ambitions. Now he may have to learn to live with them. A meeting of senior US intelligence analysts last week was unanimous in concluding that little can be done to stop Iran under Mahmoud Ahmadinejad, its volatile president, from acquiring the technology to develop the bomb. The United States lacks the intelligence for targeted airstrikes, partly because there are so many targets. Military action would also send global oil prices soaring and exacerbate America’s already intractable problems in Iraq. Mr Bush does not have to take the advice of his intelligence community, but after Iraq he would be wise to be wary.

In one sense this news is a relief because it appears to rule out the immediate prospect of further conflict. But in the longer term it will change for ever the balance of power in the Middle East. A country whose president has said that he wants Israel “wiped off the map” is not a secure home for weapons that enable him to do precisely that. The region is volatile enough without adding highly enriched uranium to the mix. If the West cannot prevent Iran acquiring nuclear weapons through a skilful containment strategy it seems highly likely that other countries in the region will join the arms race. Syria, Saudi Arabia and Egypt will be tempted to get the bomb.

Nobody wants nuclear proliferation, but the only time a nuclear weapon has been used in war was when nobody else possessed one. The arms race during the cold war led to the doctrine of mutually assured destruction, meaning no one dared to use the bomb. India and Pakistan have both acquired nuclear weapons and, if anything, this has helped to stabilise their relationship. The best policy must be to prevent the spread of weapons of mass destruction, for nuclear weapons could fall into the hands of terrorists. If other countries do get them, we can only pray they find a new sense of responsibility. If nothing else, awe at their power may stay the countries’ leaders.