The disaster of a sectarian war in Iraq between Sunni Arabs and Shi’ites came closer with bombing of a mosque in Samarra. This terrorist act was calculated to strike at the core of the belief system of Shi’ite Muslims, for the Golden Mosque is revered by Shi’ites as the burial place of the 10th and 11th imams.

Sunni Islamist extremists, known as Salafis, commonly regard such Shi’ite beliefs as heresy. Abu Musab al-Zarqawi, the Jordanian commander of the network that calls itself Al Qaeda in Mesopotamia, has made no secret of his intention to kill Shi’ites merely for being Shi’ites and has proclaimed that his strategic objective is to ignite a religious war in Iraq between the two major branches of Islam. Such a conflict would be the ultimate nightmare for Iraqis, their neighbours, and Americans hoping to foster a democratic order in Iraq.

Fortunately, the most respected senior Shi’ite ayatollah, Ali Sistani, has called for purely peaceful protest. America’s ambassador to Iraq, Zalmay Khalilzad, needs to redouble his efforts to coax Shi’ite and Sunni Arab political leaders into forming a national unity government able to isolate Islamist radicals.

The price of failing to bring Iraq’s political factions together could be a catastrophic religious war that lasts for years and spreads across the world’s most volatile region.