America must act to prevent Iraqi civil war If the Arab Spring has raised the banner of enlightened reform across the Middle East, Iraq has become a glaring exception to the trend. Since the last American troops departed, Baghdad has witnessed an explosive political crisis. Nouri al-Maliki, the prime minister, lost no time to move against his opponents and shore up his own power. Even as US forces made for the Kuwaiti border, he turned on Iraq's leading Sunni Arab politicians: Tariq al-Hashemi, the vice-president, who was forced to flee the capital to avoid arrest, and Saleh al-Mutlaq, the deputy prime minister, who was threatened with dismissal. Superficially, this might appear like the crash and thunder inseparable from managing a coalition. In reality, the sectarian element of this confrontation is what makes it so dangerous. Mr Maliki, a Shia, stands accused of thrusting aside the Sunni Arabs, who form the country's second biggest minority, in the cause of maximising his own power. If Iraq under Saddam Hussein suffered the tyranny of a dictator, the prime minister's critics allege that he is trying to impose a tyranny of the Shia majority. Mr Maliki has clearly broken the power-sharing agreement that led to the formation of the government after last year's election. In the process, he has called into question the settlement between Iraq's competing groups that helped restore a measure of stability. Under this arrangement, the Shia majority were given the prime ministership, Iraq's most powerful office, balanced by the award of the presidency to a Kurd and the vice-presidency and speakership of parliament to Sunni Arabs. Left unspoken was America's implicit role as guarantor of this settlement. Iraqis asked, sotto voce, how long it would last after US forces withdrew. The answer, we have learnt, is that its foundations were undermined within hours. Ayad Allawi, leader of the Iraqiya coalition, the largest political alliance, has warned of civil war. While he is an avowed opponent of the prime minister, his words must be taken seriously. Sunni Arabs formed the mainstay of the insurgency that followed Saddam's downfall. Their inclusion in a political settlement helped bring about the fall in violence that has allowed a degree of optimism about Iraq's future. If, however, Sunni leaders are hounded out of office, this minority might give up on peaceful politics and return to waging sectarian civil war. Avoiding this outcome will require direct American pressure on Mr Maliki. This crisis provides an early and vital test of the extent of US influence in the country that has absorbed more American blood and treasure than any other in the last decade.