The briefing was presented by unnamed "US officials" and was held 'off-camera' to preserve their anonymity. They showed examples of siezed materials which "had characteristics unique to being manufactured in Iran... Iran is the only country in the region that produces these weapons,".
Sooooo . . . that's their idea of damning evidence, hey? An 'official'-'unofficial' briefing by people who won't even be named, presenting circumstantial evidence that is impossible to verify independently (and that's the real issue here- US Military Intelligence has become a byword for obfustication and if they want to be taken seriously they will have to have verifiable evidence). No evidence was supplied that might indicate that the weapons had made their way into the hands of the militia by anything other than illicit means. Selling weapons to anyone with the money is one thing (hello BAE Systems!) but covertly supplying them to insurgents to help further their cause is quite another and the Bush administration is blatantly trying to pass the former off as the latter. One is tempted to observe that the US are- as usual- trying to get people to do as the say, not as they do. The number of incidences of the US covertly supporting insurrections against regimes they object to are beyond count (that is not an attempt to support or defend any Iranian involvment). As has been observed previously, the Shrubbery's hypocrisy knows no bounds.
More in The Guardian.
"Iran will dismiss the claims, saying it is hardly surprising there are Iranian weapons in Iraq given that the two countries fought between 1980 and 1988, and that Tehran had armed militia groups fighting Saddam Hussein."
Pretty hard for the US to argue against, methinks. If they have harder evidence they will have to present it to congress. They haven't so they haven't.
Iran has countered the accusations.