The prospect of an early US withdrawal from Iraq has receded further after an intelligence assessment warned that a pull-out by coalition forces would only lead to a further surge in sectarian violence.
The National Intelligence Estimate (NIE) on Iraq, which was presented to President George Bush yesterday, said a political reconciliation between Sunni and Shia factions is unlikely in the next 18 months.
Even the sanitised version of the report made bleak reading, concluding that a single event - the killing of a political or religious leader, for example - could plunge the country into chaos. "The possibilities have the potential to convulse severely Iraq's security environment," the report noted. The assessment represents the distilled wisdom of all 16 US spy agencies.
It was published amid more bad news for the US on the ground in Iraq itself, as the Pentagon confirmed that a military helicopter went down near the Taji air base north of Baghdad. The craft was the fourth helicopter lost over the past month, all believed to have been shot down. No details were immediately available about casualties.
"Clearly, ground fire has been more effective against our helicopters in the past couple of weeks," Gen Peter Pace, the chairman of the joint chiefs of staff, said yesterday, raising the possibility that the shooting down represented "new tactics or techniques".
The NIE document, entitled Prospects for Iraq's Stability: A Challenging Road Ahead, will only intensify the debate raging over future US policy, as Congressional Democrats - as well as some Republicans - fight Mr Bush's plan to send an extra 21,500 troops into Baghdad and al-Anbar province, where the violence is worst.
It also comes closer to admitting than any Bush administration assessment thus far that Iraq is in the grip of a civil war. Technically, say the analysts who drew up the report, the term "civil war" does not describe an extraordinarily confused situation, where insurgents are fighting US troops, Sunnis are fighting Shia, and Shia militias and factions are even fighting among themselves.
Yet, it conceded, "civil war" was an accurate reflection of aspects of the conflict in Iraq. These ingredients include the hardening of sectarian identities, displacements of civilian populations that amounted to ethnic cleansing, and "a sea change in the character of the violence". Iraq, in short, is hanging in the balance, and barring a decline in the violence and some form of political rapprochement, "we assess that the overall security situation will continue to deteriorate," the NIE stated.
Moreover, if US forces were to leave by mid-2008 - as advocated by many Democrats and the Iraq Study Group - it would "almost certainly" lead to a "significant increase" in sectarian violence.
In its published version at least, the document does not dwell on Iran's involvement, which has produced pointed warnings from Mr Bush and generated concern that the White House may be preparing for military action against Tehran.
Outside actors, the NIE said, are not likely to be the main propellents of violence, simply because of the "self-sustaining dynamic" of the internal sectarian strife. Nonetheless Iran's "lethal support" for certain Shia militias "clearly intensifies the conflict". Syria for its part is faulted for giving refuge to Baath party extremists, and for not tackling the flow of foreign jihadists into Iraq.
The report ends with worst-case scenarios if the fighting spins out of control. Three possibilities are set out: a collapse of sovereignty that would produce a de facto partition; the emergence of a Shia strongman, as the majority sect asserts its latent strength; and, finally, what the NIE calls "the anarchic fragmentation of power". This last would see "a checkered pattern of local control, with the greatest potential for instability, mixing extreme ethno-sectarian violence with debilitating intra-group clashes."