Britain and the other signatories to a treaty banning cluster bombs will have eight years in which to destroy all their stocks but are forbidden to use the weapons during that period.

However, under the terms of the convention, which was formally adopted in Dublin yesterday by 111 countries, British Armed Forces will be allowed to fight alongside American troops who are armed with cluster bombs.

The United States took no part in the treaty negotiations.

One of the key sticking points of the convention, which was published in full yesterday after 12 days of negotiations, is Article 21.

It says that armed forces of those countries signed up to the treaty “may engage in military co-operation and operations” with nations “not party to this convention”, which might fire cluster munitions in a joint campaign.

Britain’s stocks of artillery-fired M85 and helicopter-launched M73 cluster bombs are covered by the agreed definition of these weapon systems, which embraces all explosive submunitions weighing less than 20kg (44lb).

The Ministry of Defence has not revealed how many cluster bombs are held in stock and has not yet worked out what it will cost to destroy them. However, it is acknowledged that this process will run to many millions of pounds.

The treaty text says that all cluster munitions must be kept separate from other weapon systems still in operational use and should be marked “for the purpose of destruction”.

The MoD confirmed that it did not have any other cluster-type weapon systems. However, a spokesman said that development work was currently under way to produce a replacement system that would not breach the convention but would provide a capability to hit enemy armour – the principal role of the cluster bomb.

The proposed system is the ballistic sensor-fused munition (BSFM) which will be fired by the Army’s self-propelled AS90 artillery. The munitions will be dropped by parachute and use sensors to seek out enemy targets such as tanks and other armoured vehicles as they drift down. Each weapon will have two submunitions.

The Army says that this new “smart” weapon will enable gunners in the artillery regiments to target the enemy with much greater accuracy, thus reducing any “collateral damage” (civilian deaths), although it will still be an indirect-fire weapon, like the cluster bomb.

However, the BSFM will not be ready for operations until 2012, which means the Army will have a capability gap of about four years.

Yesterday’s landmark international convention obliges each signatory “never under any circumstances” to use cluster munitions, or to “develop, produce, otherwise acquire, stockpile, retain or transfer” these weapons to anyone else.

The signatories to the convention, which will need to be ratified by Parliament, are also obliged to clear and destroy the remnants of cluster munitions located in areas under its jurisdiction or control. In Britain’s case, this will entail clearance operations in southern Iraq where more than 100,000 M85 submunitions were fired by British forces in the 2003 invasion. Campaigners described the convention as “hugely significant”, despite the absence of countries such as the US, Russia and China.

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