The United States has said the United Nations must act to prevent Iraq's "active and systematic efforts" to hide its efforts to produce weapons of mass destruction.

Secretary of State Colin Powell presented tape recordings, satellite photographs and intelligence data showing Baghdad's "evasion and deception" in the face of UN weapons inspections.

	:	Powell's briefing
Images of the US briefing at the Security Council

Mr Powell warned a special session of the UN Security Council against any further delay in tackling what he called Iraq's chemical, biological and nuclear arms ambitions.

But France, a key Council member, said that inspections should continue and force should only be used as a last resort.

'Irrelevance'

"Leaving Saddam Hussein in possession of weapons of mass destruction for a few more months or years is not an option," said Mr Powell

Clearly, Saddam will stop at nothing until something stops him Colin Powell

Click here for key points of briefing

"This body places itself in danger of irrelevance if it allows Iraq to continue to defy its will without responding effectively and immediately," said Mr Powell.

But France, which has a veto in the Security Council, said that the work of the weapons inspectors had not yet run its course, and their numbers should be tripled if necessary.

"For now we must reinforce the inspection regime. The use of force can only be a final resort," said French Foreign Minister Dominique de Villepin, reacting to Mr Powell's speech.

UK Foreign Secretary Jack Straw said Mr Powell had presented the most "powerful and authoritative" case against the Iraqi regime.

Satellite photos show Iraqi deception, says Powell

Mr Straw called on the Council to "face its responsibilities" after next week's report by UN weapons inspectors.

In its first reaction to the presentation, Baghdad issued a blanket denial.

Iraqi presidential adviser Amer al-Saadi said intercepts of alleged conversations between Iraqi officials cited by Mr Powell were "manufactured".

General al-Saadi dismissed other items contained in the US dossier, and said his government would issue a fuller rebuttal on Thursday.

UN Secretary General Kofi Annan, for his part, said war could still be avoided.

"US officials have said all along that they do not believe that war is inevitable, provided that Iraq complies," Mr Annan said.

Death threats

"I cannot tell you everything I know but what I can share with you is deeply troubling," said Mr Powell.

Current Security Council

For military action: United States, United Kingdom, Spain and Bulgaria Sceptics or opposed: France, Russia, China, Germany and Syria In doubt: Angola, Cameroon, Chile, Guinea, Mexico and Pakistan Nine votes and no veto required to pass a resolution

Security Council quick guide

Mr Powell began by playing two recent tape recordings which, he said, were conversations between Iraqi military officials discussing how to block the work of UN weapons inspectors.

One man is heard telling a colleague to clear out "forbidden material", and destroy the message after it was received.

"This was part and parcel of a policy of evasion," said Mr Powell.

Mr Powell told the council that Iraqi scientists had been told by Saddam Hussein that they were not to agree to be interviewed outside Iraq, in contravention of the UN resolution.

One scientist had even been sent into hiding by the Iraqi regime, after a false death certificate was issued for him so that he could avoid being interviewed by the inspectors.

Other scientists, said Mr Powell, were threatened with death by the regime if they divulged information to the inspectors.

Photographs

Mr Powell went on to show satellite photographs which, he said, showed that evidence had been moved from military bunkers in mid-December as UN inspectors were about to visit them.

"An army of Iraqi intelligence officers" were tracking the inspectors, said the US secretary of state.

POWELL'S CASE AGAINST ZARQAWI

Heads "deadly terrorist network" in Iraq Bin Laden lieutenant Connected with Ansar al-Islam group operating in N Iraq outside Saddam's control Accused of ordering murder of US diplomat in Jordan Had medical treatment in Baghdad in May-June 2002 Some members of his group believed to be operating freely in Baghdad

Click here for more about Zarqawi

Another photograph showed lorries which, he said, were moving missiles at almost 30 sites.

"We don't know precisely what Iraq was moving," he said.

He said the Iraqis had failed to account for any of the biological and chemical warfare materials they were known to possess as a result of earlier inspections.

The Iraqi army had been told to use nerve gas, said Mr Powell, and the order would not have been given unless the gas existed.

Mr Powell presented graphics showing mobile factories for producing biological agents - there were at least seven such facilities, he said, loaded on 18 lorries.

"How can the UN inspectors hope to find these without the Iraqis coming forward?" he asked.

Mr Powell said that Iraq was continuing efforts to produce a nuclear arsenal.

He then discussed alleged ties between al-Qaeda and Iraq.

He said members of a group headed by a Jordanian al-Qaeda associate, Abu Musab al-Zarqawi, have been operating freely in Baghdad for eight months.

Meanwhile, the US is continuing its military build-up.

The Pentagon on Wednesday said 110,000 American military personnel were now in the Gulf region - thousands more reservists have been called up.