The U.S. military commander in Iraq has stepped up accusations that Iran was stoking violence in Iraq and said Tehran's ambassador to Baghdad was a member of the Revolutionary Guards Qods force.
Washington accuses the force, the elite unit of Iran's Revolutionary Guards, of inciting bloodshed in Iraq and of training and equipping militias who have attacked U.S. troops.
General David Petraeus, speaking at a U.S. military base about 30 km (20 miles) from the Iranian border on Saturday, said Iran was giving advanced weaponry to militias in Iraq.
"They are responsible for providing the weapons, the training, the funding and in some cases the direction for operations that have indeed killed U.S. soldiers," Petraeus told a small group of reporters when asked if the Iranian government was responsible for killing U.S. troops.
"There is no question about the connection between Iran and these components, (the) attacks that have killed our soldiers."
In August President George W. Bush, already at odds with Iran over its nuclear program, said attacks on U.S. troops with Iranian-supplied weapons were increasing and he had told commanders in Iraq to "confront Tehran's murderous activities".
Since then, U.S. military officers have repeatedly presented what they say is evidence of Iranian-produced arms, including the particularly deadly explosively formed projectile (EFP) bombs, being used against U.S. soldiers.
"The ambassador is a Qods force member," Petraeus said of Hassan Kazemi-Qomi, Iran's envoy to Baghdad.
He did not say how he knew this but appeared to suggest that Kazemi-Qomi was not under the U.S. military spotlight because he was a diplomat.
The Iranian embassy in Baghdad had no immediate comment.
Tehran routinely denies U.S. accusations about its role in Iraq's violence, as well as Western allegations its nuclear program is aimed at developing atomic weapons.
Bush has said he is committed to diplomacy to resolve the dispute over Iran's nuclear program but he has not ruled out taking military action.
Kazemi-Qomi has twice met U.S. ambassador Ryan Crocker in Baghdad this year for landmark talks on ways to stabilize Iraq. The discussions have made little headway, with both sides accusing each other over the violence in the country.
The U.S. military, which has poured 30,000 extra soldiers into Iraq this year to try to stem the sectarian warfare between Iraq's majority Shi'ites and minority Sunni Arabs, says the troop "surge" has helped reduce some of the killing.
But the government of Prime Minister Nuri al-Maliki has failed to push through legislation to reconcile the country's warring communities -- laws which are vital to any long-term reduction in the violence.
In Baghdad on Sunday eight people were killed in three separate bombings. On Thursday, an Iraqi Shi'ite mayor and four of his guards were killed in an attack south of the capital.
The U.S. military said the mayor was killed by an EFP.
Petraeus said Iran was supplying advanced rocket-propelled grenades, shoulder-fired "Stinger-like" air defence missiles and 240 mm rockets to militias in Iraq.
This was in addition to components used to make EFPs, a particularly deadly roadside bomb that has killed hundreds of U.S. troops in Iraq.
Petraeus also suggested there was an Iranian link in the assassination of two provincial governors in southern Iraq in August. Both were killed by roadside bombs.
"They are implicated in the assassination of some governors in the southern provinces," said Petraeus.