By Paul Reynolds BBC News Online world affairs correspondent

Before going into the detail, the general point has to be made that the case against Iraq does not depend on weapons of mass destruction, or a "smoking gun", being found.

What is required under Security Council Resolution 1441 is simply a finding that Iraq has not "fully co-operated" with the weapons inspectors.

Warheads uncovered by inspectors were never listed by Iraq

This may not be regarded as adequate by opponents of any war but it is the line strongly pursued by the United States and Britain.

The case that Iraq is not fully "co-operating" was laid out by the chief UN weapons inspector, Hans Blix, and the head of the International Atomic Energy Agency (IAEA), Mohamed ElBaradei, to the Security Council on 9 January.

News Online has seen copies of their written statements.

They followed this up with a visit to Baghdad to raise the specific points of complaint and will report back to the Council on 27 January.

As they left Baghdad they reported that Iraq had agreed to be more helpful. Mr Blix said that "a number of practical issues" had been resolved but "not all".

Missing items

The first area in dispute concerns Iraq's explanation about what happened to unaccounted-for material:

• Anthrax: Mr Blix told the Security Council that Iraq's declaration did not account for missing amounts (some 26,000 litres) of anthrax and that "Iraq's account of its production and unilateral destruction of anthrax... may not be accurate." After the talks in Baghdad, Mr Blix said this issue remained unaddressed.

• VX nerve agent: Mr Blix said to the Council that "we have found no additional information in the declaration that would help resolve this issue". The UN says that 1.5 tonnes are missing. This is also unresolved after the Baghdad talks.

• Biological growth media: Iraq imported more than it declared. Mr Blix told the Council no explanation had been given.

  Iraq has argued that it destroyed the VX, and that the anthrax and growth media were either destroyed or are no longer of any use. Mr Blix says that documents, witnesses and other evidence should be produced to support that.

• Ballistic missiles: Mr Blix said after the talks in Baghdad that a question about unaccounted-for Scud missiles (believed to number about 12) had not been resolved.

Suspicious finds

Other issues in dispute relate to unlisted materials actually found, such as missile engines and empty warheads, as well as the question of access to Iraqi scientists:

• Missiles: the Council was told that Iraq had admitted that its new al-Samoud rocket had reached 183 kilometres in a test firing - beyond the 150km limit imposed by the UN.

  Mr Blix also said that "inspections have confirmed the presence of a relatively large number of missile engines, some imported as late as 2002". These were "illegal imports". Their significance was being examined.

• 16 chemical warfare warheads: Twelve were found by the inspectors, Iraq volunteered four more. Had they been forgotten or was it evidence of deception?

• Nuclear papers: Inspectors found some technical papers in the house of a leading nuclear scientist. He says they were notes for a previously declared programme for enriching uranium. The inspectors' verdict is awaited.

• On interviews with Iraqi scientists, which are regarded as potentially the only way to get a clear picture of Iraqi operations, Mr Blix told the Security Council:

  "We do not feel that the Iraqi side has made a serious effort to respond to the request [for names] we made."

  This issue came up again in the Baghdad talks and Iraq promised to be more forthcoming. This will be a key test.

  Mr ElBaradei of the IAEA reported to the Council that while Iraq had produced two nuclear scientists asked for, they had both "requested the presence of an Iraqi Government inspector" which was not "optimum".

Proving a negative

There was better news for Iraq on the mystery of its attempted import of thousands of aluminium tubes.

The suspicion was that it wanted these for centrifuges to enrich uranium for a nuclear bomb but Mr ElBaradei's report to the Council said that the IAEA analysis "indicated that the... tubes sought by Iraq... appear to be consistent with reverse engineering of rockets" as Iraq had asserted.

The UN inspectors formally report their findings on 27 January

However, Mr ElBaradei added that the importing of such tubes was banned anyway.

It can be seen that the United States and Britain could make much of the missing material.

They could argue that Iraq has shown a pattern of limited co-operation which is designed to deceive.

Iraq, on the other hand, complains that it is being asked to prove a negative and that in the circumstances, this is an impossible task.

The assessment of the UN teams will be given to the Security Council on 27 January.