US threatens to use biggest bomb as hunt switches north

The United States stepped up the military and psychological pressure on the Baathist stronghold of Tikrit yesterday as the hunt for Saddam Hussein and leading members of his regime began to focus on areas to the north and west of Baghdad.

In what looked to be a calculated propaganda move, the Pentagon issued a thinly disguised threat to deploy – for the first time in the war – the biggest non-nuclear bomb in its arsenal, the 21,000lb massive ordnance air burst. The warning came as Allied forces continued the aerial bomb- ardment of Tikrit and the Republican Guards protecting the town.

American commanders believe that some of the regime's members may have fled north to Tikrit or west to Syria. US intelligence – using human sources and surveillance devices – was said to be reporting that the leadership had virtually disappeared. Even the hitherto relentlessly visible Information Minister, Mohammed Saeed al-Sahaf, has vanished.

Military sources at Central Command have suggested that the uniformity of the withdrawal, which extended even to the minders for foreign journalists in the Iraqi capital, implied that some form of central command and control was still operating. CIA analysts in Qatar and Langley, Virginia, are said to believe the likeliest explanation was an order issued in President Saddam's name.

The sources suggested that this was a more probable explanation than the death of the Iraqi dictator when the US dropped four 2,000lb bombs on a restaurant in Baghdad's Mansur district on Monday. Although President Saddam was reported to have entered the building shortly before the bombing, British intelligence sources have said that he escaped by minutes.

The mystery over President Saddam's whereabouts deepened when the Iraqi National Congress leader, Ahmed Chalabi, told CNN of unconfirmed reports indicating that the Iraqi President had taken refuge in the city of Baqubah, north-east of Baghdad. He said that his son Qusay had survived and "is occupying some houses in the Diyala area".

But US commanders have made clear throughout this week their close interest in Tikrit, President Saddam's birthplace and a town on the Tigris 90 miles north of Baghdad. On Wednesday Brigadier General Vince Brooks showed reporters video shots of the bombing of command and control facilities in the area. US special forces have also set up checkpoints on the main roads between Baghdad and Tikrit to prevent movement between the two cities.

Big Gen Brooks went on to say that Iraqi troops had been deployed to reinforce defences around the town, including the Adnan Mechanised Division of the Republican Guard.

General Richard Myers, Chairman of the Joint Chiefs of Staff, said ten or more Iraqi army divisions – as many as 80,000 troops – were between Baghdad and Kurdish- controlled northern Iraq.

By contrast, Major-General Gene Renuart, director of operations at US Central Command, acknowledged that there were no "substantial" ground forces in the area. The US Fourth Infantry Division, which is disembarking in Kuwait, is known to be preparing to deploy there and forward units could arrive in the area as early as next week.

Meanwhile, US operations increased around al-Quaim, a town on the Euphrates close to the Syrian border and a likely crossing point for regime members seeking to flee Iraq. General Renuart saidSpecial Republican Guard units, paramilitary forces and some regular army units were still fighting in the area but had been weakened by air strikes and attacks by special forces aimed at stopping al-Quaim from being used to launch missiles on "Iraq's neighbours".

While the general mentioned only Saudi Arabia and Jordan he is assumed to have been also referring to Israel. On Wednesday Donald Rumsfeld, the US Defence Secretary, suggested that "senior regime people are moving out of Iraq into Syria". He later qualified the remark to imply that these did not include leading figures.

But Tikrit, whose symbolism for the regime is enhanced by the fact that it was the 12th- century birthplace of Saladin, the legendary Muslim leader who defeated the Crusaders, is thought to by some experts to be the likeliest redoubt for a last stand by President Saddam. A stronghold of pro-regime loyalists, it is thought by some experts to be perhaps the one part of Iraq where there could be enough military and paramilitary forces to mount a sustained fight.

The former CIA analyst and adviser to Bill Clinton on Iraq, Kenneth Pollack, told The Washington Post that President Saddam was highly conscious of how he would be perceived by history. Therefore, he would be unlikely to leave Iraq, and would probably prefer to fight to the end in Tikrit.