Troops on the move as the world inches closer to conflict

Preparing to unleash a ferocious war against Saddam Hussein's regime, George Bush warned his country last night to be prepared for loss of life and for a conflict that ideally would be short, but that could last for some time.

The sombre message was delivered by Ari Fleischer, the White House spokesman, hours before the deadline for President Saddam to leave Iraq expired, at 01.00GMT today. The United States, he said, hoped the war would be "as precise and short a conflict as possible".

President Bush remained inside the White House as the deadline passed, without any indication from his aides as to the timing of the invasion.

"The disarmament of the Iraqi regime will begin at a time of the president's choosing," Mr Fleischer said.

But inside and outside Iraq, the sense was that the onslaught could be hours away. Allied warplanes launched new attacks on targets in the no-fly zones, and B-52 bombers prepared to depart from RAF Fairford in Gloucestershire. Long columns of British and US troops from the 250,000-strong force in the region entered the demilitarised zone separating Kuwait from Iraq.

In Baghdad, the last diplomats and United Nations workers left while members of the Iraqi parliament vowed their loyalty to the President, proclaiming their readiness for "martyrdom". The Iraqi leader gave not the slightest sign of accepting a last-minute offer from Bahrain for safe haven. Such a step would be "unthinkable", Iraqi officials declared.

At the same time, Tariq Aziz, Iraq's Deputy Prime Minister, went on television to scotch rumours that he had defected. He told reporters: "I decided to meet you ... to affirm that we are ready to fight."

It was also reported that Saddam Hussein's half-brother, Sab'awi Ibrahim Hasan al-Tikriti had sought refuge in Damascus, but there was no independent confirmation.

The Pentagon said 17 Iraqi soldiers had crossed into Kuwait and surrendered, in the first tangible result of the intense propaganda and leaflet campaign mounted by the US military to persuade ordinary troops not to resist.

Washington resumed the air of a city under siege, similar to the immediate aftermath of 11 September. There was high-level security around the White House, government buildings and other sites, to protect against a retaliatory strike by terrorists, which some officials regard as almost certain.

Earlier, President Bush met senior military and foreign policy advisers to review the final plans for an invasion, and spoke to Tony Blair on the phone for 20 minutes, mainly about a future UN resolution. Mr Bush's next public appearance will be when he tells the world he has given the order for the attack to begin.

Mr Blair, who warned Labour MPs at a private meeting that there were "difficult times ahead", told the Commons yesterday: "We will do everything we can to minimise civilian casualties and indeed maximise the possibilities of a swift and successful conclusion to any conflict." The Prime Minister, who has previously refused to endorse American calls for "regime change", said for the first time that the only way to disarm Iraq was to topple President Saddam.

"If we do remove Saddam from power, as I believe we will have to because it is the only way of disarming Iraq of weapons of mass destruction, the people who will rejoice most will be the Iraqi people, who will be free of the murderous tyrant who has done nothing but damage to his country," he said.

White House officials said the media would be given only the shortest prior notice of Mr Bush's address. If the pattern of the 1991 Gulf War holds, the first sign that war has begun will be images of missiles, bombs and anti-aircraft fire in the skies over Baghdad.

This time, the aerial bombardment that prepares the ground for invasion will be extremely punishing – an onslaught of up to 3,000 precision-guided weapons, smashing into targets in and around the Iraqi capital and other big cities.

But the exact timing has been a closely guarded secret. An important factor would be the weather and the threat of further sandstorms.

US military officials told the New York Times that there were naval clashes early yesterday around the Iraqi port of Basra, after Iraqi fishing boats headed towards Allied warships. The Americans opened fire, fearing a suicide attack.

In a boost for the Allies, the Turkish parliament seemed close to giving its approval for the US to use its airspace.