The first major effort by the George W. Bush administration to substantiate its case that the Iranian government has been providing weapons to Iraqi Shiites who oppose the occupation undermines the administration's political line by showing that it has been unable to find any real evidence of an Iranian government role.

Contradicting recent claims by both Secretary of State Condoleezza Rice and Secretary of Defence Robert Gates that U.S. intelligence had proof of Iranian government responsibility for the supply of such weapons, the unnamed officials who briefed the media Sunday admitted that the claim is merely "an inference" rather than based on a trail of evidence.

Although it was clearly not the intention, moreover, the briefing revealed for the first time that the Iranians and Iraqis detained by U.S. forces in recent months did not provide any evidence implicating either the Iranian government or the Islamic Revolutionary Guards in the acquisition of armour-piercing explosive devices and other weapons by Iraqi Shiite groups.

Chairman of the Joint Chiefs of Staff Gen. Peter Pace further underlined the weakness of the administration’s case by declaring Monday in an interview with Voice of America, "It is clear that Iranians are involved, and it's clear that materials from Iran are involved," he continued, "but I would not say by what I know that the Iranian government clearly knows or is complicit."

In the end, the administration presentation suggested that there could be no other explanation for the presence of Iranian-made weapons than official government sponsorship of smuggling them into Iraq. But in doing so, they had to ignore a well-known reality: most weapons, including armour-piercing projectiles, can be purchased by anyone through intermediaries in the Middle East.

The briefing displayed a number of weapons or photographs of weapons said to have been found in Iraq, including what were called "explosively formed penetrators" (EFPs), which the officials said were smuggled into the country by the Islamic Revolutionary Guard "Quds Force". The RPG-7s and 81 mm mortar rounds shown to reporters did indeed have markings showing that they had been recently manufactured, and there is no reason to doubt that those weapons were manufactured in Iran.

The argument for Iranian official responsibility assumes that such weapons are so tightly controlled that Shiite groups could not purchase them in small numbers on the black market in Iran, Syria or Lebanon. It is well documented, however, that the Shiites have resorted to black market networks to obtain EFPs.

An article in Jane's Intelligence Review last month by Michael Knights, chief of analysis for the Olive Group, a private security consulting firm, reports that the British discovered that there was indeed an organisation in Basra engaged in arranging for the purchase and delivery of imported EFPs and that it was comprised entirely of police officials, including members of the Police Intelligence Unit, the Internal Affairs Directorate and the Major Crimes Unit. They found that members of the organisation followed no specific Shiite faction, but included members from all the factions in Basra.

The Washington Post quoted one of the U.S. officials at the briefing as saying that there was no "widespread involvement" of the Iraqi government in supplying weaponry, thus implicitly conceding that some elements of the Iraqi government officials are indeed involved in the weapons traffic.

By insisting that the Iranian government was involved, the Bush administration has conjured up the image of a smuggling operation so vast that it could not occur without official sanction. In fact, as Knights points out, the number of EFPs exploded monthly has remained at about 100, which clearly would not require high level connivance to maintain a flow of imports.

The power point slides presented to the press in Baghdad ended with a slide that essentially confirms that the evidence points not to official sponsorship of cross-border weapons smuggling but to private arms trafficking networks.

The slide, which can be viewed on the Talking Points Memo website, includes the curious statement that information from detainees "included references to Iranian provision of weapons to Iraqi militants engaged in anti-coalition violence." That formulation carefully avoids stating that any of the information implicated Iranian officials. Furthermore the slide's six bullet points, representing the concrete "highlights" of the information, fail to make reference to any official Iranian role in the smuggling of weapons across the border.

In fact, the slide reveals that the smuggling is handled by what it calls "Iraqi extremist group members", not by the Qods Force of the Iranian Revolutionary Guards. The oral presentation accompanying the power point indicated that the smuggling had been carried out by "paid Iraqis", without specifying who was paying them, according to the New York Times report.

The final bullet point of the slide says, "Qods Force provides support to extremist groups in Iraq by supplying money, training and propaganda operations." But its silence on the question of supplying weapons to groups in Iraq represents a serious blow to the credibility of the administration's line.

The EFPs used against U.S. and British troops in Iraq were the centrepiece of the briefing. But the anonymous U.S. officials did not claim that the finished products have been manufactured in Iran. Instead they referred to machining of EFP "components" -- referring to the concave metal lids on the devices -- as being done in Iran.

That position parallels the testimony by Gen. John P. Abizaid on Mar. 16, 2006 to the Senate Armed Services Committee, which claimed only that "sophisticated bomb-making material from Iran has been found in improvised explosive devices in Iraq".

It also raises an obvious question: if Iran has the technical ability to supply the complete EFPs, why are only components being smuggled into Iraq?

The absence of shipments of complete EFPs suggests that the components that have been smuggled in have been manufactured in small workshops outside the official system. Knights, the most knowledgeable and politically neutral source on the issue, says these components could have been manufactured by a "small handful of external bomb-makers". He notes that the only source to claim that the Iranian defence industry is the source of the EFP components is the opposition National Council of Resistance of Iran.

The U.S. briefers argued that EFPs are not being manufactured within Iraq. The New York Times quoted a "senior military official" as saying that they had "no evidence" that the machining of components for EFPs "has ever been done in Iraq".

But Knights presents evidence in Jane's Intelligence Review that the Iraqi Shiites have indeed manufactured both the components for EFPs and the complete EFPs. He observes that the kind of tools required to fabricate EFPs "can easily be found in Iraqi metalworking shops and garages."

He also notes that some of the EFPs found in Iraq had substituted steel plates for the copper lining found in the externally made lids. Knights calculates the entire production of EFPs exploded thus far could have been manufactured in one or at most two simple workshops with one or two specialists in each -- one in the Baghdad area and one in southern Iraq.

"I'm surprised that they haven't found evidence of making EFPs in Iraq," Knights told IPS in an interview. "That doesn't ring true for me." Knights believes that there was a time when whole EFPs were imported from outside, but that now most, if not all, are manufactured by Iraqis.

Taking into account the false notes struck by the anonymous officials, the damaging admissions they made and the absence of information they needed to make a case, the briefing appears to have been a serious setback to the administration's propaganda campaign. It will certainly haunt administration officials trying to convince Congress to support its increased aggressiveness toward Iran.

*Gareth Porter is an investigative historian and journalist specialising in U.S. national security policy. His latest book, "Perils of Dominance: Imbalance of Power and the Road to War in Vietnam", was published in June 2005.