arch/ive/ief (2000 - 2005)

George W Bush will make a rare address on American primetime television tomorrow to outline the case for a war to disarm Saddam Hussein.

In his weekly radio address yesterday, the President said that war might now be "unavoidable" and described Iraq's weapons programme as a "grave and growing" threat to the United States.

The comments follow a sharp increase in bombing missions by American and British warplanes against Iraq's military infrastructure in the no-fly zones.

The President will deliver the 20-minute address in Cincinnati, Ohio, a Midwestern venue that appears to have been chosen to show that he is preparing the American heartland for the likelihood of war. His aides are comparing its importance with his televised remarks immediately after the September 11 attacks.

The increase in raids by Allied aircraft on targets that include command and control facilities has come as negotiations drag within the United Nations Security Council over a new round of weapons inspections.

The inspections are seen by many members of the Security Council as a last chance to avoid war with Iraq. As the diplomacy continues, however, the bombing raids are taking place at a level that suggests a covert conflict has already begun.

The northern and southern no-fly zones in Iraq, set up in 1991 to protect Iraq's Kurdish population and patrolled by the United States and Britain, are witnessing what amount to the first battles of a new war between Iraq and Allied forces.

Last week an Iraqi cabinet meeting was called by Saddam to discuss the attacks, which are undermining the regime's strategy of delaying conflict through wrangling over the terms of new weapons inspections.

A joint statement issued after the meeting angrily declared: "The fever and croaking of those who harness themselves to attack the Arab nation has increased in these past days; this despite Iraq's agreement on the return of the inspectors."

During August and September more air raids were carried out by Allied warplanes against Iraqi military installations than in the previous seven months of the year combined.

British and American planes patrolling the southern and northern no-fly zones in Iraq carried out 12 bombing missions in August and a further 13 in September. During one attack on an Iraqi airbase, 12 American and British aircraft dropped 25 bombs on an Iraqi command and control centre, 240 miles southwest of Baghdad.

Another raid targeted the Iraqi air force Southern Sector Operations Centre at Tallil, 160 miles from Baghdad, which co-ordinates all Iraqi air defences south of the capital.

US and British military officials acknowledge that command and communications headquarters in Saddam's air defence systems and military airfields are now being routinely targeted along with anti-aircraft batteries and mobile radar vehicles. "The scope may well have been broadened," said one US military official.

In one concentrated attack, radar systems at Basra airport were destroyed along with parts of the civilian terminal building, causing protests from government officials in Baghdad.

In a television broadcast the Iraqi government accused America and Britain of "escalating their policy of spite and evil against our great Iraq. In violation of international laws and conventions, the US ravens of evil carried out a fresh sinful attack, targeting Basra international airport".

US Central Command officials in Tampa, Florida, said that raids on Basra airport were aimed at military radar installations and were "in response to hostile acts" towards allied planes.

Donald Rumsfeld, the US Defence Secretary, said last week that the increased number of attacks was in response to repeated firing at Allied planes by Iraqi forces in the northern and southern no-fly zones. In the two weeks since Iraq agreed to the return of weapons inspectors, the Pentagon said, Iraqi forces had fired on American and British aircraft 67 times.

Thousands of leaflets have been dropped over the southern no-fly zone in Iraq, warning in Arabic that "no tracking or firing on [Allied] aircraft will be tolerated". A US military official said: "We're saying: 'Don't shoot at us because if you do you could die.' "

Mr Rumsfeld said: "Here you have US and British planes flying daily to enforce the UN resolutions, putting their lives at risk, day after day for years. With each missile launched at our air crews, Iraq expresses its contempt for the UN resolutions."

US military officials privately acknowledge that the new level of bombing of air-defence sites in Iraq will create valuable "air corridors" for an Allied attack, if agreement on weapons inspections cannot be reached.

Russia, France and China are resisting Mr Bush's demand that a new UN resolution should include the threat of force if Saddam obstructs inspections of sites such as presidential palaces, where access has previously been restricted.

On Friday the UN's chief weapons inspector, Hans Blix, said that he would wait for a new resolution before making final arrangements for his team to go to Iraq.