By Rageh Omaar BBC correspondent in Baghdad

Within the space of a momentous 24 hours - the importance surrounding the work of UN weapons inspectors has become even more critical.

There is no doubt that the whole political dynamic of this crisis has changed, and peace now seems that much farther away.

It is for the UN inspectors to discover, verify and report the truth General Amer Al Sa'adi, Iraqi adviser

The United States and Britain always feared that the weapons inspections programme would drag on, empty of any new information or discoveries.

But their description of Iraq's voluminous declaration of it's weapons programmes as a "material breach" has changed everything.

No surprise

In effect, London and Washington have now introduced a tripwire for military action if there is so much as a hint of Iraqi non-co-operation.

Such threats and warnings can have come as no surprise to the Iraqi government.

UN inspectors have visited nearly 150 suspected sites

For them, this is no more than American and British attempts to dictate events to the UN Security Council. General Amer Al Sa'adi, an adviser to the Iraqi President Saddam Hussein laid down the gauntlet to the UN.

"It is for the UN inspectors to discover, verify and report the truth," he said, adding that Britain and America "have nothing they can pin on Iraq".

Weapons inspectors have been conducting nearly four weeks of operations, having visited nearly 150 suspected sites.

But no problems have been reported and inspectors say they have received good co-operation.

Intelligence information

But unfettered access is no longer the central issue. It is now about access to critical information.

Up to 20,000 scientists were reportedly involved in Iraq's weapons projects

London and Washington continue to insist that they have evidence that Iraq is continuing to hide prohibited weapons programmes.

If that is the case, the inspectors need to find them. And clearly, they are going to need the necessary intelligence that Britain and the United States say they have.

But there is one other issue which up until now has attracted little attention, but which could prove to be a defining moment in this crisis.

Interviewing scientists

By the end of the year, UN inspectors expect to receive a list of top scientists that they want to question from the Iraqi authorities.

UN Resolution 1441 makes clear reference to Iraqi scientists.

The mood among ordinary Iraqis is that conflict is certain

It says the inspectors may, at their discretion, conduct interviews with Iraqi scientists inside or outside the country.

It also says the inspectors may facilitate the travel of those interviewed and their family members outside of Iraq.

But there are several significant loopholes in this wording. Firstly, how many scientists are involved?

Some reports speak of up to 20,000 scientists having been involved in Iraqi weapons programmes over the past 20 years, other independent analysts say the figure is far less.

The fact that the UN has asked Iraq to draw up the list may be an indication that nobody really knows the accurate figure of scientists involved, and their roles.

Mood of doom

Furthermore, what exactly constitutes a family.

Does it mean the western interpretation of the nuclear family - perhaps up to 10 relatives?

Or does it mean the extended family as it is viewed in Iraq and the rest of the Arab world, which could involve up to 40 or 50 relatives?

One can be sure that Iraq will demand long explanations and clarifications on both these points.

But for ordinary Iraqis all of this is academic. Amongst them there is an overwhelming mood that conflict is not just inevitable but certain.

The events over the past few days will have only hardened this view.