Shia Islamist leaders have demanded an autonomous federal state across oil-rich southern Iraq today only four days before a deadline for agreeing a new constitution.
Minority Sunni Arab leaders, as well as a spokesman for the Shia-led coalition government, rejected the idea, and it is unclear whether the split would hold up delivery of a draft text that Washington hopes can help quell the Sunni insurgency.
At an mass rally in Najaf, heartland of Shia Islam, the leader of the Supreme Council for the Islamic Revolution in Iraq (SCIRI) Abdul Aziz al-Hakim, increased pressure on his opponents from ethnic and religious minorities as the head of his party's military wing derided central government in Baghdad.
Shia account for about 60 per cent of Iraq's people, and the issue of autonomy raises major concerns for the country's ability to hold together and for the division of its oil wealth.
Sunni Arabs, dominant under Saddam Hussein, other minorities and secular Shias wary of religious rule have been opposing the idea of a constitution that would allow southern Shia the kind of autonomy now enjoyed de facto by Kurds in the north.
SCIRI, long close to Shia Iran, inspires strong emotions among Iraqis. Opponents accuse it and the Badr movement of fomenting religious vigilantism - charges they deny.