The slaughter of scores of Sunnis at a mosque northeast of Baghdad Friday has underscored the threat of a full-scale sectarian civil war, even as Washington prepares to escalate its military intervention in Iraq and potentially extend it to neighboring Syria.

The attack took place in a village near Baquba, the capital of Iraq’s Diyala province, about 75 miles northeast of Baghdad. A suicide bomber blew himself up in the mosque and then gunmen mowed down worshippers fleeing the building. Conflicting reports put the number of dead at between 64 and 75.

The attack was attributed to a Shi’ite militia allied with the Shia-dominated government in Baghdad. It was believed to have come in response to a roadside bombing carried out during a recent recruitment campaign by the militia.

The incident has ominous implications for the US strategy for defeating the Islamic State of Iraq and Syria (ISIS), which has overrun close to a third of Iraq, and reasserting US hegemony over the oil-rich country.

This strategy has included both a resumption of direct US military intervention in the form of some 90 airstrikes against ISIS positions, the bulk of them around the strategic Mosul dam, and the effecting of “regime change” in Baghdad with the ouster of Prime Minister Nouri al-Maliki and his replacement by another Shi’ite politician from the Dawa party, Haider al-Abadi.

Maliki, who was installed by the US occupation in 2006, was seen as too identified with a hardline sectarian policy against the country’s Sunni minority. This policy had its roots in the divide-and-conquer tactics of Washington, which, after overthrowing Saddam Hussein, recast Iraqi politics along sectarian lines.

The US aim was to use Abadi to attract support from sections of the Sunni leadership and thereby undercut the Sunni popular insurgency that has allowed ISIS to drive the Iraqi military out of the country’s north and west, including Mosul, Iraq’s second largest city.

Friday’s massacre appeared to seriously undermine this strategy, however, with the new speaker of parliament, Salim al-Jubbouri, responding with an announcement that the Sunni parliamentary bloc which he leads would boycott Abadi’s new government. There is a clear threat that the violence in Iraq and the mobilization of sectarian militias will send the country spiraling back to the level of mass killing that erupted under the US occupation in 2006-2007.

In the wake of ISIS’s brutal videotaped beheading of American journalist James Foley, the war rhetoric in Washington has sharply escalated.

At a Pentagon press conference on Thursday, Secretary of Defense Chuck Hagel described ISIS as “an imminent threat to every interest we have, whether it’s in Iraq or anywhere else.”

US Joint Chiefs of Staff chief Gen. Martin Dempsey, referring to US air strikes against the Islamist fighters in Iraq, indicated that the Pentagon is at least contemplating a far wider regional war. He said that the Islamist fighters: “can be contained, not in perpetuity. This is an organization that has an apocalyptic, end-of-days strategic vision and which will eventually have to be defeated... can they be defeated without addressing that part of their organization which resides in Syria? The answer is no. That will have to be addressed on both sides of what is essentially at this point a nonexistent border.”

Virtually in the same breath, however, Dempsey added that he was not “predicting” that air strikes “will occur in Syria, at least not by the United States of America.”

Similarly, Ben Rhodes, a deputy national security advisor, told National Public Radio Thursday that US operations against ISIS would not be restricted “by geographic boundaries,” but added that the administration has not “made decisions to take additional actions at this time.”

These assessments followed earlier statements by President Barack Obama referring to ISIS as a “cancer” that would have to be “extracted” and by Secretary of State John Kerry that the organization “must be destroyed.”

All of the American officials have spoken in terms of persuading other governments, particularly in the Middle East, to collaborate with US operations in the region. General Dempsey said that US strategy called for “a coalition in the region that takes on the task of defeating ISIS over time.” Among those sought for this “coalition” is the ruling monarchy in Saudi Arabia, a patron of Islamic fundamentalism, which in the last two weeks has beheaded at least 19 people, roughly half of them for committing nonviolent offenses.

Support for ISIS and other Islamist militias operating inside Syria has come from Saudi Arabia, Qatar and Kuwait, all among the closest US allies in the Arab world, with Washington’s blessings. This was part of the imperialist-orchestrated war for regime change against the government of President Bashar al-Assad.

The Islamist forces in Syria had been further strengthened with arms and fighters from Libya, where the Obama administration had carried out a similar war to topple Muammar Gaddafi through NATO air strikes and the use of Islamist militias as proxy forces on the ground.

Now the results of these imperialist interventions, from the war of aggression against Iraq in 2003 to the wars in Libya and Syria, have come together in the debacle for US policy represented by the ISIS advance and the collapse of the Iraqi security forces trained and armed by the Pentagon.

What policy Washington will pursue is by no means clear. The administration has proposed funneling $500 million worth of arms and support to the so-called “moderates” of the Free Syrian Army, an entity that is widely reported as non-existent on the ground in Syria, where the principal militias fighting the Assad government are ISIS and other Islamist factions led by the Al Qaeda-affiliated al-Nusra front.

There is clearly an emerging debate within imperialist circles over whether a wider war should be launched with the combined aims of eradicating ISIS and overthrowing Assad in Syria, or whether the US and its allies should quietly shelve their quest for regime change in Damascus and tacitly act in concert with the Syrian security forces against the Islamists.

This dispute found explicit expression in a column published Friday in the British Daily Telegraph by the former British ambassador to the US, Christopher Meyer, entitled, “Our national interest demands the mother of all U-turns.”

Meyer writes that while Washington is beginning to discuss air strikes against ISIS bases in Syria, he could not “imagine the US would risk their bombers and drones being shot down by Syrian fighter aircraft or ground-to-air missiles,” and that it would need to coordinate its military actions with the Assad government. “This in turn would require a political somersault of truly dramatic proportions,” he continued. “In the face of Isil [ISIS], a common enemy, the US and probably the UK would be working with a regime we have been trying to unseat for the better part of three years.”