So what do 'the twin menaces' posed by Iraq really add up to?

Its nuclear programme is stagnant and its chemical arsenal hardly constitutes a threat

As he returned from Washington yesterday, the Prime Minister, Tony Blair, spoke of the "twin menaces" of Iraq's weapons of mass destruction and its links with terrorism. Supplying the proof will fall to Colin Powell, the US Secretary of State, when he addresses the UN Security Council on Wednesday.

Mr Powell will be seeking to achieve what the weapons inspectors have so far failed to do: demonstrate to the world that Baghdad is not only hiding weapons of mass destruction (WMD), but is actively trying to develop them.

Carefully co-ordinated leaks from Washington have suggested he will reveal intelligence – possibly satellite photographs – showing Saddam Hussein's regime has been concealing mobile biological weapons laboratories. Newsweek reported at the weekend that he would publish tapes of conversations among Iraqi officials which show they have been "hiding stuff" from the inspectors. The Secretary of State, it is said, will also detail its purchase of materials for making chemical, nuclear and biological weapons.

So far, however, US attempts to demonstrate Iraq's evil intentions have been ambiguous at best. The administration has repeatedly claimed, for example – most recently in George Bush's State of the Union address – that Baghdad had bought aluminium tubes to restart its nuclear programme. Not only did nuclear scientists dispute the allegation that the tubes could be used for such a purpose, Mohamed ElBaradei, head of the International Atomic Energy Agency, thought they were more likely to be employed in non-nuclear rockets, which Iraq is allowed to possess as long as they do not exceed a range of 150 kilometres, or just over 90 miles.

So how much of a threat does Iraq pose? From the report presented by the chief weapons inspector, Hans Blix, on Monday and previous UN inspections, we can assume Iraq has tactical chemical weapons. The release of an unauthenticated Iraqi document, detailing the regime's procurement of protective suits and nerve agent antidote for its elite troops, supports this assertion and indicates that it will attempt to use them to defend itself.

Iraq may also have longer-range Scud-type missiles that could deliver chemical or biological weapons. We can assume that this strategic capability is relatively limited, however, as Washington and London would not be proposing to attack Iraq if it had developed a cred- ible deterrent. In that case, as with nuclear-armed North Korea, a more diplomatic approach would be adopted.

The primary chemical weapons-related issue raised by Dr Blix concerned Iraq's production of the nerve agent VX. Considered one of the most deadly weapons of its type due to its toxicity (it is easily absorbed through the skin or respiratory system) and its persistence (it can continue to contaminate an area for up to a week), VX kills its victims by paralysing the nervous system, which ultimately results in respiratory and heart failure. Although Iraq declared that it had unilaterally destroyed its stocks of VX nerve agent, Dr Blix stated: "Unmovic has information that conflicts with this account."

One of the most important unanswered questions concerns a large amount of the precursor agent needed to produce VX. Baghdad claims that it was destroyed either by bombing during the 1991 Gulf War or unilaterally in the aftermath of that conflict.

Iraq also continues to insist that it unilaterally destroyed its stocks of biological warfare agents in the summer of 1991. But Dr Blix noted that Iraq had provided "no convincing evidence for its destruction", and that there are "strong indications that Iraq produced more anthrax than it declared, and that at least some of this was retained after the declared destruction date". A quantity of bacterial growth media, which could be used to produce about 5,000 litres of concentrated anthrax, also remains unaccounted for.

But it is not enough for a country wishing to develop an effective WMD capability to produce only chemical or biological agents: it also needs an effective method of delivering them against an enemy. The Blix report highlighted the fact that some 6,500 chemical bombs, which could deliver 1,000 tonnes of chemical agent, were still unaccounted for.

The discovery of the 12 chemical warheads for 122mm rockets also raised questions. Although Baghdad claimed that these had been purchased in the 1980s and subsequently overlooked, Dr Blix noted that the bunker in which they were stored was relatively new and that the discovery pointed to "the issue of several thousands of chemical rockets that have been unaccounted for". These warheads are used on relatively short-range (around 12.5 miles) unguided rocket artillery systems, normally multiple rocket launchers that can rapidly carpet a target area with conventional explosives or, in this case, agents such as VX.

Rockets, artillery shells and, to a lesser extent, aerial bombs are generally considered to be "tactical" – intended for battlefield use – rather than "strategic" delivery systems, which are designed to inflict maximum damage on civilian population centres. Ballistic missiles, which are extremely hard to intercept, provide the mainstay of any strategic arsenal. Any country with WMD and long-range missiles enjoys a virtually uncontestable deterrent against attack.

The chief inspector pointed out that Iraq had tested both Al Samoud 2 and Al Fatah missiles with a range in excess of 150km. He also noted that Iraq had the infrastructure to produce missiles "capable of significantly greater ranges than 150km".

The Al Samoud programme was specifically designed to comply, or be seen to comply, with UN resolutions, and consequently probably does not have a range much in excess of 200km. The Al Fatah missile is Iraq's modified version of the Soviet Scud missile. With a range of up to 650km, it constitutes the backbone of Iraq's strategic capability. While Dr Blix gave no indication of numbers, Western intelligence reports suggest Iraq may have up to 20 such missiles. Iraq fired 81 conventionally armed Al Fatah missiles during the Gulf War. The number of launchers Iraq has managed to maintain is also significant, as it dictates the rate at which they can be fired: Baghdad would want as intense a barrage as possible to increase its chances of saturating Israel's missile defences.

None of Iraq's missile warheads or bombs is particularly efficient at delivering chemical or biological agents. There is little evidence to suggest that Iraq has managed to obtain warheads that explode in mid-air, spraying the agents over a wide area. Most chemicals are destroyed on impact and biological agents are even harder to store and deliver. Intelligence reports have indicated, however, that Iraq has been attempting to convert jet training aircraft into unmanned drones that could spray a chemical agent over a wide area in the same way that agricultural crop-dusting aircraft work. While such drones may solve the problem of finding volunteer pilots, they would still be vulnerable to sophisticated air defences.

What does all this add up to? Iraq clearly has the ability and desire to produce nasty chemical and biological agents, but its ability to use them in anything apart from close combat is doubtful. Its nuclear programme is stagnant; it probably has some forbidden missiles, but again they hardly constitute an imminent threat. If Mr Powell is to prove that war is the only solution, he will have to produce some truly dramatic intelligence this week.

Jeremy Binnie is Middle East editor of Jane's Sentinel Security Assessments