By Jonathan Marcus BBC defence correspondent

Is a war to topple Saddam Hussein inevitable?

The US administration is set on Saddam Hussein's removal from power

Reading much of what comes out of the Bush administration, one might be forgiven for giving the answer as a blunt "yes".

The only question may be who rejects the weapons inspectors first: Will it be the Iraqis, who regard their activities as too intrusive, or the Bush administration, which sees them as not being intrusive enough?

The Bush team has a strong scepticism about the whole idea of inspections.

This is in large part based upon Iraq's past track record of thwarting the UN, alleged evidence that Iraq is preparing for another deception campaign and the perceived centrality of weapons of mass destruction in Mr Hussein's strategic thinking.

But there also does seem to be a strong element of "seizing the moment" in the Bush team's behaviour.

Preparations underway

The events of 11 September altered the internal dynamics within the Bush administration and the hawks now have the president's ear.

It is hard to escape the feeling that the whole debate about the resumption of inspections is seen, by a least some in Washington, as simply a hoop that has to be jumped through on the way to securing the Iraqi leader's removal.

Viewed in this light the war has not quite started.

But the preparations are well underway.

Additional troops and equipment have been moved to the Gulf, ostensibly for exercises.

US Central Command, or Centcom - the headquarters that would run any new Gulf War - is also deploying a good portion of its staff to the Gulf state of Qatar.

This move, also first described as an exercise, is now being described as more of a prudent precaution.

It also brings the headquarters staff closer to the potential theatre of operations.

Impending action

And over the next six to eight weeks a whole series of other "prudent" precautions may be taken.

Iraq's air defences are slowly being warn down

Watch the movement of key US Navy carrier battle groups, for example, always a good indicator of impending action.

Britain's preparations too should be monitored. But its contribution could be light amphibious or air mobile forces that could be mobilised and moved rapidly if required.

Indeed, in one sense the war could be said to have already started, since, in the US and British-enforced no-fly zones over northern and southern Iraq, hostilities have never really ended.

The first shots?

According to a recent Pentagon briefing, patrolling US and Allied jets have been fired on by the Iraqis more than 400 times this year alone.

Often the US response is robust - warplanes attacking the source of the fire or the radars that control it.

But in mid-September the US Defence Secretary Donald Rumsfeld announced that US tactics in the no-fly zones had changed.

Pilots are now allowed to attack fixed structures associated with Iraq's air defences, such as communications sites or relay stations.

Thus Iraq's integrated air defence system is slowly being worn down.

These could be the first shots in the campaign to remove Saddam Hussein.

The war may not have started, but the preliminary skirmishes are well underway.