The outbreak of sectarian violence has Iraq’s delicate political process hanging in the balance.The main Sunni Muslim bloc has pulled out of talks to form a new government, blaming the main Shi’ite alliance for the unrest. Some Sunnis attended a crisis meeting hosted by the president today while others threatened to boycott the political process altogether, as they did during interim polls last year. Iraq’s top Shi’ite cleric, Grand Ayatollah Ali Al-Sistani, has made a rare appearance on television to emphasise the need for calm. He has called for protests but also restraint. More than 130 people have been killed since Wednesday’s bombing of the Shi’ites sacred Golden Mosque in Samarra. Authorities say most of the victims are Sunnis who have died in a string of revenge attacks on dozens of Sunni mosques in Baghdad and Basra. With the violence showing no sign of abating, Iraq’s leaders have increasingly warned of the dangers of a civil war. Tit-for-tat killings are already the norm among Iraq’s deeply divided communities. Iraq’s authorities have cancelled all police and army leave and extended curfew hours in Baghdad and other cities.