Where are those Iranian arms in Iraq?

The United States military command in Iraq continues to talk about an alleged pipeline of Iranian weapons to Iraqi Shi'ites opposing the US occupation, implying that they have become dependent on Iran for indirect-fire weapons and rocket-propelled grenades (RPGs).

But US officials have failed thus far to provide evidence that would support that claim, and a long-delayed US military report on Iranian arms is unlikely to offer any data on what proportion of the weapons in the hands of Shi'ite fighters are from Iran and what proportion comes from purchases on the open market.