The battle between Sunni and Shia Muslims for control of Baghdad has already started, say Iraqi political leaders who predict fierce street fighting will break out as each community takes over districts in which it is strongest.
"The fighting will only stop when a new balance of power has emerged," Fuad Hussein, the chief of staff of Massoud Barzani, the Kurdish leader, said. "Sunni and Shia will each take control of their own area." He said sectarian cleansing had already begun.
Many Iraqi leaders now believe that civil war is inevitable but it will be confined, at least at first, to the capital and surrounding provinces where the population is mixed. "The real battle will be the battle for Baghdad where the Shia have increasing control," said one senior official who did not want his name published. "The army will disintegrate in the first moments of the war because the soldiers are loyal to the Shia, Sunni or Kurdish communities and not to the government." He expected the Americans to stay largely on the sidelines.
Throughout the capital, communities, both Sunni and Shia, are on the move, fleeing districts where they are in a minority and feel under threat. Sometimes they fight back. In the mixed but majority Shia al-Amel district, Sunni householders recently received envelopes containing a Kalashnikov bullet and a letter telling them to get out at once. In this case they contacted the insurgents who killed several Shia neighbours suspected of sending the letters.
"The Sunni will fight for Baghdad," said Mr Hussein. "The Baath party already controls al-Dohra and other Sunni groups dominate Ghazaliyah and Abu Ghraib [districts in south and west Baghdad]."
The Iraqi army is likely to fall apart once inter-communal fighting begins. According to Peter Galbraith, former US diplomat and expert on Iraq, the Iraqi army last summer contained 60 Shia battalions, 45 Sunni battalions, nine Kurdish battalions and one mixed battalion.
The police are even more divided and in Baghdad are largely controlled by the Mehdi Army of the radical nationalist cleric Muqtada al-Sadr and the Badr Organisation that has largely been in control of the interior ministry since last May. Sunni Arabs in Baghdad regard the ministry’s paramilitary police commanders as Shia death squads.
Mr Hussein gave another reason why the army is weak. "Where you have 3,000 soldiers there will in fact be only 2,000 men [because of ghost soldiers who do not exist and whose salaries are taken by senior officers]," he said. "When it comes to fighting only 500 of those men will turn up."
Iraqi officials and ministers are increasingly in despair at the failure to put together an effective administration in Baghdad. A senior Arab minister, who asked not to be named, said: "The government could end up being only a few buildings in the Green Zone."
The mood among Iraqi leaders, both Arabs and Kurds, is far gloomier in private than the public declarations of the US and British governments. The US President George W Bush called this week for a national unity government in Iraq but Iraqi observers do not expect this to be any more effective than the present government of Prime Minister Ibrahim al-Jaafari. One said this week: "The real problem is that the Shia and Sunni hate each other and not that we haven’t been able to form a government."
The Shia and Kurds will have the advantage in the coming conflict because they have leaders and organisations. The Sunni are divided and only about 30 per cent of the population of the capital. Nevertheless they should be able to hold on to their stronghold in west Baghdad and the Adhamiyah district east of the Tigris. The Shia do not have the strength and probably do not wish to take over the Sunni towns and villages north and west of Baghdad.
Though the Kurds have long sought autonomy close to quasi-independence, their leaders are worried that civil war will increase Iranian and Turkish involvement in Iraq. Mr Hussein said he feared that civil war in Baghdad could spread north to Mosul and Kirkuk where the division is between Kurd and Arab rather than Sunni and Shia.
Already Baghdad resembles Beirut at the start of the Lebanese civil war in 1975, when Christians and Muslims fought each other for control of the city.