The report by the CIA and the Defense Intelligence Agency comes as the Bush administration faces pressure to prove its justification for the war -- that Saddam had to be disarmed of nuclear, biological and chemical weapons programs that were an imminent danger.

"Examination of the trailers reveals ... an ingeniously simple, self-contained bioprocessing system," the report says. "Both trailers we have found probably are designed to produce BW agent in unconcentrated liquid slurry."

"BW" is for "biological weapons." US officials believe Iraqi leaders were interested in developing mobile fermentation units for such weapons.

There is no evidence the two trailers were ever actually used to make biological weapons, the intelligence officials said. Officials also said they did not expect to find biological agents inside the trucks, which they said the Iraqis probably had decontaminated.

The report's conclusions key on evidence from an Iraqi source, a chemical engineer who claims to have managed one of the mobile production plants.

That source has also identified photographs of the captured trailers, the new report says. Three other Iraqi sources also described efforts by Saddam's government to build a mobile biological weapons plant.

Intelligence officials who briefed reporters Wednesday on condition of anonymity, said they had considered and discarded possible legitimate uses for the trailers, ranging from the production of hydrogen to pesticides. The trucks would not be able to do any of those very well, they indicated.

"The Iraqis had a motivation to inefficiently produce a biological agent," said one intelligence official. "They had no motivation to inefficiently produce anything else."

Captured Iraqi scientists have said the vehicles were for producing hydrogen for weather balloons in support of artillery. The report acknowledges the trailers could be used to make hydrogen but says the effort would be inefficient compared with widely available commercial hydrogen generation systems.

A technical analysis of the trucks showed they could be used, though inefficiently, to complete the early steps of creating a biological weapon, intelligence officials said. Based on information from the source, they believe each truck was part of a two-truck or three-truck system that could create a finished agent.

Each of those multiple-truck systems -- the CIA believes Iraq had around seven -- could produce a few pounds of biological agent a month. The intelligence officials said they do not know which agent -- anthrax, botulinum toxin or others -- might have been involved.

The first truck was captured at a checkpoint run by US-backed Kurdish militia in northern Iraq and then was turned over to American forces. The second, already looted, was found by US forces in early May at the al-Kindi Research, Testing, Development and Engineering facility in the northern city of Mosul.

A third trailer, found in Baghdad, is a mobile toxicology laboratory from the 1980s, the report says. It could have legitimate uses or be part of a weapons program.

Information about the trailers, based largely on the Iraqi engineer's description, was a key component of Secretary of State Colin Powell's February 2003 presentation to the United Nations regarding Iraq's alleged weapons programs.

The Pentagon had previously reported the trailers' discovery and its suspicions that they were mobile labs.

The trailers have already been inspected by US and British technical experts and a group of scientists from coalition countries. Another team of international experts arrived in Iraq Saturday to inspect the evidence and will probably need a few more days, US officials in Iraq said Monday.

Meanwhile, former Sen. Sam Nunn urged Congress to investigate whether the argument to go to war in Iraq was based on distorted intelligence. He said there was a possibility that President Bush's policy against Saddam influenced the intelligence that indicated Baghdad had weapons of mass destruction.

The CIA and other US intelligence agencies have begun a review of their prewar views of Iraq.

Nunn, a Georgia Democrat and former chairman of the Senate Armed Services Committee, now heads the nonprofit Nuclear Threat Initiative. He spoke from Paris, where he met leaders about money to fight weapons proliferation.

(China Daily May 29, 2003)