Senior Democrats in the United States have urged the Bush administration to be cautious about accusing Iran of fomenting violence in Iraq.
They were speaking after US officials in Iraq said they had evidence that Iran was providing weapons to Shia militias who attacked the US military.
US claims the bombs were smuggled from Iran cannot be independently verified.
Democratic Senator Chris Dodd said the Bush administration had tried to falsify evidence before.
"I'm looking at this report with a degree of scepticism," he said.
More on BBC
Also see "Evidence Grows That White House Planned To Release Cooked Intel On Iran" on ThinkProgress
Most US papers do not question the evidence... like The Charlotte Observer and some think: "Israel Needs A Preemptive Nuclear Strike Against Iran"