So far, despite numerous tip-offs and searches, the 180,000 troops on the ground have found no chemical or biological weapons since the start of the war a month ago.

This has led to some international skepticism about the banned weapons, whose alleged presence in Iraq was the main reason given for the US-led invasion.

But coalition officials say they are certain they will find the weapons and insist that, once they do, they will take every precaution to demonstrate they did not plant the evidence.

"Once the military find something, we are going to get specialists to comply fully with international verification," a British military spokesman said at the Central Command's war headquarters in As-Saliyah, Qatar.

US Defense Secretary Donald Rumsfeld himself expressed concern some governments or individuals might continue to doubt that Iraq stockpiled weapons of mass destruction (WMD) even if coalition troops found some.

He said on Thursday that controls were in place to ensure evidence is untainted, but lamented that that "will not stop certain countries and certain types of people from claiming, inaccurately, that it was planted."

Military officials say the search will be lengthy and painstaking, as troops and experts try to put together what they believe is a jumble of pieces of evidence, most of which are yet to be found.

They believe that in a bid to hide the weapons from UN inspectors, the Iraqi government took them apart and hid the bits and pieces all over the country.

"It's now a thousand-piece jigsaw puzzle," said the British spokesman, who asked not to be named.

US Brigadier-General Vincent Brooks concurred. "In this case you also have to find the pieces of the puzzle and then put them into proper relationship with other pieces that are there," he said.

"At this point in time we know that there are delivery systems ... some have been encountered," he said, also pointing to the discovery of atropine injectors that could be used to treat someone exposed to chemical agents.

In their rush to Baghdad, the US-led forces bypassed numerous areas, and made only cursory assessments of some potentially suspicious locations.

But the search is now starting in earnest.

Officials at the Pentagon say 1,000 US experts will scour the country to find and secure the weapons the United States claims Saddam produced.

Three dozen former UN arms inspectors have been asked to join the Iraq Survey Group, which also includes US government experts and officials. They will be with several hundred US troops already assigned to the weapons hunt.

Military officials say assistance from Iraqis is crucial to point the search in the right directions.

"And this is really where we need the assistance of the Iraqi population and regime leaders that might have some knowledge. And as time goes on and we get more access to individuals and more access to information, we get pointed in new directions," said Brooks.

SPACE.WIRE