The prime minister is said to be increasingly concerned that the number of his own MPs who oppose military action could top 100 just as British troops reach the Gulf.

Labour MPs told Blair last night that going to war with Iraq without finding firm evidence against Saddam Hussein could provoke a repeat of Suez, the botched military invasion by Britain and France that ended the career of Sir Anthony Eden, the then prime minister.

Clive Soley, a senior Labour MP and former chairman of the parliamentary Labour party, said: "There is a danger of getting into a conflict without the support of the country or parliament. You don't want to go down that route. That is what happened at Suez when the prime minister fell and the nation was divided." Cabinet ministers have privately expressed similar concerns.

Advisers are urging Blair to change his tone when he addresses the parliamentary party on Wednesday, by saying that any military action will be aimed at "liberating" rather than "invading" Iraq — words used by President George W Bush last week.

Blair will seek to reassure the MPs over military action, and his aides said last night that Bush would not "go for it" without a clear reason.

"He will be saying that Saddam has got to be disarmed but that it will be done via the UN route," said a senior Downing Street official. "We have got a very clear strategy through diplomacy and inspections."

However, one cabinet minister said the prime minister was "more likely than less likely"
to back Bush even if UN weapons inspectors did not uncover unequivocal evidence against Saddam.

Yesterday the aircraft carrier Ark Royal, carrying 800 crew including 100 marines, left Portsmouth for the Gulf. It is the first of 15 warships and a submarine in a British naval taskforce that will comprise 5,000 navy personnel and 3,000 Royal Marine commandos. A row was brewing over whether it would be able to defend itself from air attack because it has no Harrier jets on board.

British ground forces are also due to begin departing for the Gulf this week. Preparations are being made for a further Commons statement by the prime minister and Geoff Hoon, the defence secretary, as
tanks and artillery are assembled in Germany to be shipped to Kuwait. Up to 150 Challenger tanks, modified for desert conditions, will be put on chartered car ferries. The MoD is taking troops off firefighting duties to prepare for desert warfare. The 3rd Battalion the Parachute Regiment, based in Essex, has been issued with desert kit in readiness for duties in the Gulf.

The move comes amid a threatened wave of strikes by firefighters beginning on January 21 which could go on for "weeks or months", according to Andy Gilchrist, general secretary of the Fire Brigades Union.

America this weekend issued deployment orders to 35,000 more troops, which will take its military strength in the Gulf to up to 120,000 by the end of January. In a further escalation of pressure on Saddam, the Pentagon has sent e-mails to Iraqi generals urging them to defect and warning them not to use chemical or germ weapons against allied forces.

Thousands of messages have also been sent to Iraqi leaders and military personnel since Thursday urging them to give up and to dissent. If they do not, the messages warn, the Americans will go to war against them.

An American official said the campaign was "just the beginning of a psychological warfare campaign" to convince the Iraqi leadership they cannot win a war against America and its allies. The Iraqis were reported last night to have hit back by blocking some of the e-mails.

The messages include instructions to the e-mail recipients to contact the United Nations in Iraq if they want to defect. The programme was developed by military and intelligence agencies in recent weeks, according to American sources.

Washington is also threatening to reveal its evidence that Iraq is lying about its lack of weapons of mass destruction if the UN inspectors' report to the security council at the end of this month fails to offer any reason to go to war.

Colonel Muammar Gadaffi, the Libyan president, dismissed reports that Saddam Hussein might flee Baghdad for exile in Libya. "Don't delude yourself into believing such legends," he said in Tripoli. "I think Saddam will never leave Iraq and he will die a martyr there."

The left-wing Labour MP George Galloway has urged British arms workers to sabotage supplies of weapons and ammunition for a war on Iraq by going on strike.

Additional reporting: Jonathon Carr-Brown

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