A US military official leveled new accusations against Iran on Monday, asserting Iranian government involvement in a January, 2007 attack that killed five American soldiers in Iraq. The charges are the latest in a campaign to increase pressure on Iran, while laying out a rationale for possible future military action.

Brigadier General Kevin Bergner, the lead spokesman for US forces in Iraq, said that interrogations of prisoners in Iraq had provided evidence of Iranian involvement in a January raid in the city of Karbala. He accused Iran of using the Lebanese group Hezbollah as a “proxy” to help train Iraqis to attack US forces.

These allegations are based on statements Bergner said were made by Qais Khazali and Ali Musa Daqduq, both of whom were captured in Iraq by the US military in March.

Bergner said that Khazali has admitted to planning the Karbala attack, and that Daqduq admitted to being a member of Hezbollah. Bergner said that the two prisoners “state that senior leadership within the Quds force knew and supported planning for the eventual Karbala attack that killed five coalition soldiers.”

He added, “Our intelligence reveals that the senior leadership in Iran is aware of this activity.” When asked by a reporter, “Do you think it’s possible that [Iranian leader Ayatollah Ali Khamenei] doesn’t know?”, Bergner replied, “I think that would be hard to imagine.”

Bergner said that the Iranian Revolutionary Guard Quds Force has “funded, trained and armed” Shiite groups operating in Iraq. “Quds Force, along with Hezbollah instructors, trained approximately 20 to 60 Iraqis at a time” at camps near Tehran, he said. “The Iranian Quds force is using Lebanese Hezbollah essentially as a proxy, as a surrogate in Iraq.”

The US has been escalating accusations against Iran for several months, but the statements by Bergner represent the first time that top Iranian leaders have been accused so directly of helping plan specific attacks on US forces. The statement also represents the first time that Hezbollah has been directly accused of involvement in Iraq.

New York Times reporter Michael Gordon, himself a supporter of the Iraq war, was quick to draw the implications of Bergner’s statements. “In effect,” he wrote, “the United States is charging that Iran has been engaged in a proxy war against American and Iraqi government forces for years.” Clearly, Washington is alleging an Iranian “proxy war” in order to establish a “self-defense” rationale for launching military strikes against Iran.

When the Karbala raid happened in January, US officials were quick to blame Iran, despite the absence of any serious evidence for this claim. The operation was too complex to have been carried out by Iraqi insurgents operating on their own, the Bush administration asserted, so it was likely that Iran was involved.

There were vague suggestions that the raid was intended to capture American forces to be used as bargaining chips for the return of five Iranian diplomats captured, and still held, by the US military. Four of the five American soldiers killed in the attack died after first being captured by the assailants.

There are many reasons to doubt the story of Iranian direction of the Karbala raid. It took place at a convenient time for the Bush administration—only a week after Bush’s January 10 speech announcing plans for a “surge” of US forces in Iraq. In the same speech, Bush accused Iran of supporting Iraqi insurgents, and threatened to retaliate with military force.

The raid was carried out by about a dozen people who were waved through US military checkpoints because they were wearing US military uniforms, driving in a US-style convoy, and spoke English. The New York Times reported at the time that sections of the Iraqi government were discussing the theory that American mercenaries were behind the raid. There were a number of possible motives for staging an attack, including the most direct: that it could be used to increase threats against Iran. (See: “Unanswered questions about the Karbala raid”).

The statements that the US military says have been made by Khazali and Daqduq were given after months of incommunicado imprisonment, during which the two were likely abused. Bergner’s statements on Monday were the first acknowledgment from the US that Daqduq had even been captured. After a prolonged period of interrogation, the military now claims it has produced stronger evidence to back up what it had clearly wanted to conclude from the beginning.

In addition to the charges over the Karbala raid, the US government continues to assert high-level Iranian involvement in supplying weapons to Iraqi insurgents. These claims, first laid out in February 2007, were immediately questioned by the chairman of the Joint Chiefs of Staff, Peter Pace. Last month, US Defense Secretary Robert Gates announced that Pace would not be nominated to serve another term.

Also last month, Gates accused Iran of sending weapons to the Taliban in Afghanistan. In language similar to Bergner’s comments on Monday, Gates said at the time that “it is difficult to believe” the alleged transfer of weapons to Afghanistan “is taking place without the knowledge of the Iranian government.”

These accusations followed shortly on comments by Senator Joseph Lieberman that the US should “be prepared to take aggressive military action against the Iranians.”

Iran may be involved in supporting groups in Iraq, though the Iranian government has strenuously denied any support for Iraqi insurgents. At the same time, Iran has accused the US of supporting oppositional groups within Iran that aim to overthrow the government. The US is promoting the Mujahedin e-Khalq (MEK), which operates under US protection in Iraq near the border with Iran. MEK is still classified by the US State Department as a terrorist organization for its past role in assassinating Iranian and American officials.

An escalation of rhetoric against Iran may have a number of different motives. The US is currently pushing for a new round of United Nations sanctions against Iran and has faced resistance from Russia and China. Russian President Vladimir Putin visited with Bush on Monday, and Iran was one of the topics under discussion.

Behind this diplomatic offensive, however, prominent sections of the political establishment favor military action against Iran. Unsubstantiated allegations of involvement in Iraq and Afghanistan, together with accusations that Iran is pursuing a nuclear weapons program, are being prepared as potential pretexts for any such decision.