Hans Blix wrote to Iraqs leader last week, reminding him of his obligation under the UN Security Council resolution to allow his inspectors to speak to those who had been involved in the clandestine programme to produce weapons of mass destruction.

The United States, which believes that this is the best way of uncovering where Saddam hides his secret weapons, has drawn up its own list of wanted Iraqi scientists. They include Rihab Taha, the woman known as Dr Germ, who trained as a microbiologist at East Anglia University and is one of the leading figures in Saddams biological warfare research programme; Jaffar Dhia Jaffar, regarded as the father of Iraqs nuclear weapons programme, who was educated in Britain; Hazem Ali, a brilliant virologist who earned a PhD in Britain; and Mahdi Obeidi, an expert in uranium enrichment.

If Saddam fails to meet Dr Blixs demands, he could be accused of being in material breach of the UN resolution, providing President Bush with a possible reason for launching a military attack.

The Bush Administration fought hard to get the Security Council to empower inspectors to meet Iraqi scientists alone and to move them and their families out of the country, if necessary. Dr Blix has made clear that the UN will not serve as an abduction agency for potential defectors, but the inspectors may be able to use their new powers to find and possibly relocate scientists who have fallen from favour.

Among them is Abdul Nasser Hindawi, a founder of Iraqs bio-weapons programme, who was arrested as he tried to flee the country in 1998 and is thought to be in jail. Although his information will be four years out of date, he could provide useful historical data to cross-check with Iraqi declarations.

Yesterday, after initial judgments in Washington and London that the Saddam declaration on weapons of mass destruction was seriously incomplete, British military plans were accelerating. The Ministry of Defence has drawn up plans to charter commercial shipping to transport heavy equipment to the Gulf. It is the latest move indicating Britains growing preparations for war with Iraq.

However, ministers are still waiting for the Americans to make up their minds about the contribution that they want from Britain. The top option is still the deployment of an armoured formation, consisting of a reinforced brigade of about 12,000 troops, equipped with Challenger 2 tanks, self-propelled AS90 howtizers and multiple-launch rocket systems.

However, if there were a short timescale, defence sources said, the Government might be forced to choose to send a Royal Marine commando battle group on board HMS Ocean, the helicopter carrier, which can take a maximum of 800 marines.

HMS Ocean could join HMS Ark Royal, the aircraft carrier, which is due to sail for the Gulf next month as part of a long-planned mission. For her new overseas mission, HMS Ark Royal will be accompanied by HMS Marlborough, a Type 23 frigate, HMS Liverpool, a Type 42 destroyer, a nuclear-powered submarine and two Royal Fleet Auxiliary vessels, Fort Victoria and Orangeleaf.

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