THERE IS no doubt that Western opinion is being softened up for a US or Israeli strike against the Iranian centrifuges at Natanz. “Can anyone within range of Iran’s missiles feel safe?”, screams a full-page advertisement in the International Herald Tribune, displaying a map of the Eurasian land mass with Iran at its centre.

As part of the softening-up come the justifications, as false as the ones that preceded the Iraq war, but more disgraceful second time round. Here are the counter-arguments.

First, it needs to be trumpeted that a military strike now would be illegal under international law. The UN Security Council would never authorise it, since Iran has not breached the terms of the nuclear non-proliferation treaty that allows every signatory to develop nuclear energy for peaceful use. However, the hawks no longer even talk about the need to get Security Council approval — this is the measure of the damage to international law that Bush and Blair have inflicted.

The United States (or Israel) would claim it was acting in self-defence. But by long-established customary law a pre-emptive strike is justified only to defend against an “imminent and certain” attack. True enough, what happens tomorrow is never certain, but if another country’s troops start massing at one’s frontier that would be pretty good evidence of hostile intention. To claim the right of self-defence against a threat that may or may not emerge in five years’ time is to claim the right to wage aggressive war whenever one chooses. This was one of the two grounds on which Nazi leaders were convicted and executed at Nuremberg.

John Reid, the Defence Secretary, has recently been arguing that the right of pre-emption should be turned into the right of prevention, “rather than waiting for the next threat to come along”. If one happened to “learn” that a threat was being developed, would it not be one’s duty to zap it before it became actual? The answer is “no”. The more “potential” the threat, the less transparent it will be, the more flawed one's intelligence, and the more scope leaders will have to manipulate public opinion.

If Iraq taught us anything it should have been this. Tony Blair at first stuck to the accepted justification for a pre-emptive strike by claiming that Iraq was an immediate threat (the notorious “45 minutes”). When that was revealed as phoney, he fell back on the argument that Iraq “would have” acquired a WMD capability had we not overthrown Saddam Hussein. Such arguments allow unscrupulous leaders to make war on a whim.

To return from Mr Reid’s science fiction to earth: the technology of making nuclear weapons is not obscure. The Iranians claim to have enriched uranium to the “3.5 per cent level”. This is enough to use as nuclear fuel, but nowhere near enough for nuclear weapons. That requires up to 90 per cent enrichment, with 50 to 100 kilograms of it to make a single bomb. The Iranians say they have 164 centrifuges. But thousands would be needed to get a significant amount of weapons grade uranium. Experts say it would take five years or more to produce an atomic bomb from domestic processes.

The biggest danger of nuclear proliferation is not that rogue states will learn how to enrich uranium enough to build nuclear weapons but that already enriched uranium stocks will leak out to terrorist groups. A terrorist group that obtained 50kg of highly enriched uranium would probably be able to make a nuclear device. But it could make it anywhere — in a garage in London, for instance. The answer to this is not to bomb Iraq, but to reduce such stockpiles (mainly in Russia and the United States) to a minimum, and make sure they are under iron control.

People who support military action ask: how do we know that Iran isn't lying when it says that its uranium enrichment programme is intended only for civilian use? Surely, this is a clear case for invoking the precautionary principle: the risk may be slight but the consequences of ignoring it may be catastrophic. But no one is arguing that the risk should be ignored. The Nuclear Non-Proliferation Treaty now also allows for intrusive inspections. Hans Blix has written: “If you want a control system that gives a maximum of assurance, you can . . . require that inspectors have the right to go almost anywhere, any time, and demand any kind of documents.” Iran has accepted this protocol and operating under it the International Atomic Energy Agency has found no evidence that it is developing a weapons programme. However, the protocol could be strengthened for states such as Iran whose leaders make Hitlerian pronouncements.

Given that it is possible, though difficult, to put in place a series of checks on Iran's nuclear ambitions, our leaders need to weigh very carefully the equivocal comfort that a so-called preventive strike may buy against the massive costs of mounting one. It is as certain as it can be that a strike against Iran would inflame Muslim hatred throughout the Middle East and beyond. It would interrupt oil supplies and disorganise the world economy. It would swell the insurgency in Iraq, multiply the numbers of “terrorists” and strengthen their determination to exact a terrible vengeance, especially on Israel. It would be against every counsel of prudent statesmanship. The danger is that we will drift into war because we lack the will and imagination to create institutions to make peace safe.

“The threat posed by Iran has been grossly exaggerated” will be debated tomorrow at the Royal Geographical Society in one of a series of Times debates. www.intelligencesquared.com

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