Michael Quinlan and Lewis Dunn: The next big threat will be biological

We must find a way to prevent any use of these fearsome weapons.

Scientific knowledge in biology is advancing at an extraordinary rate and across a huge span. The coming century is bound to see an explosion of its possible applications. The potential for good is massive; but it is not exclusively benign. Just as in the last century chemistry and nuclear physics generated new weapons capable of inflicting harm beyond previous imaginings, so can the biological advance.

The September 11 reminder of global vulnerability, coupled with the US anthrax scare, has underlined the need to tackle the threat of biological weapons. Their development, possession and use are banned by the 1972 convention to which the great majority of states are party. However, it contains no effective provision for checking on observance: the Soviet Union and Iraq are known to have cheated, and up to a dozen other states are suspected of having or seeking a biological armoury.

The possession of these weapons is much harder to check on than nuclear ones. Materials open to malign exploitation are more diverse, less distinguishable from those for peaceful use and more easily produced than in the nuclear field; and facilities that could be used to build a destructive capability are less unique, less costly and less conspicuous.

The US administration has walked away from the attempt to shape a compliance protocol for the 1972 convention. Other countries deplore this dismissal of an enterprise on which the international community had laboured for years; but the administration judges that the draft could not offer enough assurance to justify the costs and risks involved.

However, the issue cannot rest there, leaving a treaty of no more than exhortatory force as the only international defence against this frightening potential. So what is to be done? The most promising approach lies in moving away from the mindset of most global arms control efforts, which have concentrated on the possession of weapons. Ultimately, what matters most is whether weapons are used. We should continue to do whatever we can to impede and stigmatise the possession of biological weapons, but we should now focus upon preventing their use.

Deterrence through capacity for fearsome retaliation already gives the US homeland a strong shield against overt state use of such weapons, but that is not the only scenario of concern to the international community, or to the US itself. Deterrence is not provided only by the existence of massive military force - it is enhanced by clarity about what will not be tolerated, by certainty of response (though attempts to predetermine its form are not always wise), by international legitimacy and support for effective response, and by the penalties displayed. The US and its allies could lead action to strengthen worldwide deterrence of biological weapons in all these respects.

What is needed is that the widest possible international constituency (preferably assembled around a security council resolution) should make a commitment to treat any use of weapons prohibited by the 1972 convention as a crime against humanity, beyond excuse; to regard any regime guilty of it, or of sheltering or supporting perpetrators, as having forfeited legitimacy; to pursue any such regime's leaders and any other participants individually as criminals; and to reverse any advantage secured by the crime, and succour its victims.

No state could easily oppose the thrust of such an undertaking. The main risk is that either idealist naivety or ill-disposed manoeuvring might try to load it with extra baggage, for example seeking to extend it to chemical or nuclear weapons (several Middle East states will not foreswear chemical weapons while Israel has nuclear ones; and nuclear weapons are too deeply embedded in the current structure of international security to be dealt with like this). Such demands would merely ensure that nothing gets done.

Action on these lines could not eradicate the threat of biological weapons, but it would strengthen deterrence (and reduce the attractions of acquisition). Saddam Hussein and others would have to reckon with a greater likelihood of severe penalty not only for use but also for tolerance or support - hard to keep dependably concealed - of terrorist use. That is a contribution worth making to filling the vacuum in international strategy against biological weapons.

The concept of international commitment to act against use of prohibited weapons could be applied elsewhere. It might help to deal with Iraq's possession of weapons debarred by UN resolution - and it would be less fraught with difficulty (over legitimacy, international support, efficacy and aftermath management) than the forcible deposition of Saddam. But that belongs to another discussion.

· Michael Quinlan is a former permanent under-secretary of state at the Ministry of Defence. Lewis Dunn is senior vice-president of the US-based Science Applications International Corporation.