The White House released a statement on September 11 saying that "The United States will hold the regime in Tehran accountable for any attack that results in injury to our personnel or damage to United States Government facilities."
The full White House statement reads.
Over the past few days, we have seen life-threatening attacks in Iraq, including on the United States consulate in Basra and against the American embassy compound in Baghdad. Iran did not act to stop these attacks by its proxies in Iraq, which it has supported with funding, training, and weapons. The United States will hold the regime in Tehran accountable for any attack that results in injury to our personnel or damage to United States Government facilities. America will respond swiftly and decisively in defense of American lives.
The short statement appears to represent a departure from US rhetoric on the role of Iranian-backed groups in Iraq, including the Hashd al-Shaabi or Shia militias that form the Popular Mobilization Forces (PMF). It is part of a wider recognition in Washington about the role of Iran in supporting militia groups in Iraq and the threat they pose to US interests in light of the new Iran policy. The administration is in the midst of pressuring Tehran and the tensions over post-ISIS Iraq are key to that pressure. But the White House has not fully explained this policy.
This statement holds Tehran directly responsible for the acts of its "proxies." This doesn't name the PMF as the proxy and doesn't name any of the groups that make up the PMF as proxies, such as Asaib Ahl al-Haq, Kata'ib Hezbollah or Badr. The US consulate in Basra may have been targeted on September 7 during the unfolding violence when protesters also targeted the Iranian consulate. Different reports said Grad rockets or Katyushas were fired toward the airport where the consulate is. The US put out statements condemning the violence and attacks on diplomats.
"The U.S. Consulate General in Basrah expresses its deep concern about the violence in some of the recent demonstrations and deeply regrets the lives lost and injuries sustained by protesters and security forces this summer. We express our solidarity with the citizens of Iraq, our community, during this difficult time. We support the right of Iraqis to peacefully assemble, to request services from their government, and to express their views. We call on all Iraqis to respect the right of peaceful protest and to respect public and private property."
The US Department of Defense Inspector General looking at the Coalition (CJTF:OIR) has increasingly warned that Iranian-backed groups represent a serious threat to the US in Iraq. But this represents a direct challenge to Tehran to control its proxies. The key point is " stop these attacks by its proxies in Iraq, which it has supported with funding, training, and weapons." Then, "The United States will hold the regime in Tehran accountable for any attack that results in injury to our personnel or damage to United States Government facilities."
Taken together this is a serious warning to Tehran. It comes amidst the crises in Iraq as coalitions maneuver for power and as Prime Minister Haider al-Abadi has challenged the PMF, seeking to reduce the role of Abu Mahdi al-Muhandis of Kata'ib Hezbollah. After the IRGC fired rockets at Koya on September 8 the US is also looking at what might come next.
One hurdle Washington faces is that the PMF was incorporated into Iraq's official security forces since 2016 and that as such they are part of the Interior Ministry. Untangling those that are accused of being proxy forces with those that are officially part of the government is difficult. The US-led Coalition is still supporting Iraq and its army as part of an advise and assist mission, which includes training. The US Congress in its new NDAA mandated that no training or support end up with the IRGC or Iranian-backed militias in an attempt to prevent the PMF benefiting via the Iraqi government from US support. But with the PMF's own party coming in second in the elections and seeking political power, the next step may be difficult.