Don't misunderstand America's motives: it is fear, not greed, that drives Mr Bush

Saddam has kept his distance from al-Qa'ida because he knows that those he feeds today will bite him tomorrow

The age of public myth has delivered two absolute truths. First you must believe that Tony Blair is the poodle of George Bush. Second, the war on Iraq is all about oil and the greed of big corporations. The first is hogwash. So is the second. Both stand in the way of sane analysis of the crisis over Iraq. But they are important myths because a great many people believe them and because we are in danger of missing the real dangers in the coming conflict.

Lets deal first with myth number one. Tony Blair is not a poodle or a Rottweiler or any other kind of canine except maybe for some kind of dog with a good nose for sniffing out trouble. Together with Colin Powell he has been among the most influential voices pressing George Bush to go the route of the UN, something the American President was mightily disinclined to do some months back. Had he not done so, we would be on our way to war by now.

As for the "it's all about oil" theory, this succeeds only if you ignore the really big picture. Control of or access to the Iraqi oilfields might be one of the beneficial spin-offs from the point of view of American corporations, but it's not Bush's main motive. Nor is the coming conflict about getting revenge on Saddam because he outlasted and humiliated Bush's father. As for the idea that its all a plot to rid Israel of its enemies in the Middle East... a tempting scenario, but again only a secondary consideration. No administration is going to risk the lives of thousands of its soldiers to secure the Iraqi oilfields or to stage a pre-emptive strike on behalf of Israel.

Getting the oil and protecting Israel would be regarded by the White House as positive "by-products" of a US invasion, but the real motive is much more fundamental. It has to do with fear. That was what the Republican electoral victory was about, and it was why Congress gave Bush the most generous blank cheque in history when it voted on Iraq. The Middle East is seen as being filled with mortal threats to American security. Any US President who is not relentless in hunting the country's perceived enemies would be politically finished.

The best exposition of the American position to date came in a document outlining America's strategic response to the post-11 September world, unveiled last month by the White House. The document – the most significant statement of American policy since John F. Kennedy's ill-fated "bear any burden" inaugural address – made clear that George Bush wasn't going to take the blame for being slow to respond to terrorist threats. This document stressed the "path of action" and said America could not be defended by "hoping for the best".

But the key phrase, the one that brings us closer to an understanding of the motives behind the looming attack on Iraq, comes further down the page. It speaks of the greatest threat in the future coming from "the crossroads of radicalism and technology", in other words from the fundamentalist carrying the suitcase nuclear bomb or the aerosol can full of nerve gas.

The terrorism of the future will be hi-tech and relatively low-cost, delivered by terrorists for whom personal survival isn't an issue. It is harder to combat, because once the delivery system – a suitcase, an aerosol can, a phial of liquid – is in the hands of the terrorist, he can wait and choose his time and place to attack. He does not need the kind of large infrastructural support base demanded by guerrillas or urban bombers such as those of the IRA or Eta.

Thus the intelligence services are left without organisations to penetrate or informers to recruit. All that is needed is one dedicated terrorist with a weapon small enough to stick in his anorak pocket or, at its biggest, in his rucksack. Because he does not belong to an organisation that is trying to co-ordinate a political goal, there is no worry about the timing or scale of attack, no political leadership worrying about the potential PR effects of the violence. In fact, the bigger and more ruthless and terrifying, the better.

In a war where, according to Osama bin Laden, "there are no innocent victims", planning is much easier. If all targets are legitimate, you simply find a crowd and detonate or spray. None of that time-consuming nonsense about telephoning warnings or making sure that there aren't too many civilians about.

But what has any of this to do with Iraq? The US does not accept the word of Middle East specialists who say that Saddam's desire to develop weapons of mass destruction is solely linked to the balance of power in the region and his worries about restive populations in the north and south of Iraq. The post-11 September view – which is shared by Britain –- is that Saddam might one day share some of his weapons capability with the followers of Osama.

The problem with this analysis is that past performance doesn't offer too much in the way of supporting evidence. Saddam has no qualms about using these weapons to commit mass murder against his own people, but the question that the White House has yet to answer is why would he want to hand over such a capability to the fundamentalists? Those Saddam armed to attack America would, sooner or later, get around to attacking a man they regard as part of the rot in the Middle East. Saddam has kept his distance from al-Qa'ida not only because he fears the retribution of the West, but also because he knows that those he feeds today will bite him tomorrow.

We are now in a position where war is inevitable if Saddam does not give up his weapons. The weapons he insists he does not have. By 8 December, he must produce a list of those weapons. There is ample opportunity here to start frustrating the inspectors. He could provide a list of so-called "dual use" items (ie chemicals and compounds that might be used in the making of weapons or might have a perfectly innocent application). The really dangerous matériel is probably stored under public buildings all over Iraq, widely dispersed and so harder to locate.

After receiving the list, it will be up to Hans Blix to test whether it is indeed a full and true account. We can expect Mr Blix to stick rigidly to the letter of the UN resolution; in other words he won't cut Saddam any slack. If Blix does declare Iraq in material breach of the resolution, the Americans and British will listen to the other Security Council members but will start the build-up to war. This remains the most likely scenario for the months ahead.

I mentioned at the beginning that the myths about the motives for this war were dangerous because of their tendency to blind us to real danger. Civilian and military casualties could be substantial in this war. But there is a much longer-term cost. Just how many young men will be prompted to join the forces of Bin Laden if Iraq is attacked and defeated? What is worrying is that this cost is hardly ever mentioned in our analysis of the conflict. George Bush is acting to protect his own people, but in doing so he may find the ranks of his enemies are greatly swollen.

The writer is a BBC Special Correspondent