Across northern Iraq people are voting with their feet. In and around Mosul, the third-largest Iraqi city, some 70,000 Kurds have fled their homes so far this year. Many have run away after receiving an envelope with a bullet inside and a note telling them to get out in 72 hours. Others became refugees because they feared that a war between Arabs and Kurds for control of the region was not far off.
"There is no solution except the division of the province," said Khasro Goran, the powerful Kurdish deputy governor of Mosul. He believes that all the Kurds in the province want to join the Kurdistan Regional Government (KRG), which under the federal constitution is almost an independent state.
Violence in Mosul, a city of 1.75 million people, is not as bad as in Baghdad or Diyala province, claims Mr Goran, who is also head of the Kurdistan Democratic Party (KDP) in Mosul, during an interview with The Independent inside his heavily fortified headquarters. This is not saying a great deal, since he added that 40 to 50 people were being killed in Mosul every week.
"Two officials from the KDP working in this building were shot dead outside their homes a few days ago," said Mr Goran, an urbane, highly educated man who spent 11 years in exile in Sweden and speaks five languages. He has been the target of eight assassination attempts, in which several guards have been killed.
It was only possible for me to go to Mosul because Mr Goran sent several of his bodyguards in two cars to pick me up in the Kurdish capital, Arbil. Travelling at high speed into Mosul, they pointed to the remains of the headquarters of the Patriotic Union of Kurdistan, which had been destroyed by a large suicide bomb in a Volvo in mid-August. The blast killed 17 men, mostly soldiers on guard. Fearing a similar attack, the KDP had just added another concrete blast wall to its already impressive defences.
The fate of Mosul, the largest city in Iraq in which Sunni Arabs are in the majority, may determine how far Iraq survives as a single country. The proportion of Arabs to Kurds in the province and city is much disputed.
There is no doubt that the Arabs are in a majority of around 55 per cent in the province, but they angrily dispute the Kurdish claim to make up a third of the 2.7 million population. When an Arab MP in parliament in Baghdad claimed this week that the Kurds made up only 4 per cent of the population of the city, all the Kurdish MPs staged a walk-out in a fury.
At the moment nobody wholly controls Mosul, one of the oldest urban centres on the planet, sprawling along both banks of the Tigris river. The 2nd Iraqi Army Division is based in the city, and the 3rd Division is outside, each 15,000-strong, and both of them are at least 50 per cent Kurdish, and with Kurdish commanders. But the Americans, fearful of the Sunni Arab reaction, have forbidden the army to patrol too aggressively.
If the Kurds have the army, the Arabs have the police. There are 16,000 policemen in the province, and 6,000 in the city. The Kurds regard them with the greatest suspicion. As we drove to the KDP headquarters, one of the Kurdish bodyguards told me to "hide your notebook and pen if we stop at a police checkpoint, because we don't trust them". The Kurds have long accused senior police officers of being crypto-Baathists, sympathetic to the insurgents.
The US experience in Mosul has not been happy. During the first year of the occupation General David Petraeus, the US commander of the 101st Division, tried to conciliate the many officers and officials of Saddan Hussein's regime who came from Mosul. In the long term the experiment failed. When US marines stormed Fallujah in November 2004, most of the police in Mosul resigned, and insurgents captured 30 police stations and $40m (#21m) worth of arms almost without firing a shot. The US was forced to call in Kurdish peshmerga fighters to retake the city.
The US and Kurds still co-operate. The Americans are highly reliant on Kurdish intelligence to search for guerrillas. But they are also conscious that a recent confidential Pentagon poll leaked to ABC television showed that 75 per cent of Sunni Arabs in Iraq supported armed resistance. The US forces, who used to have four bases in the city, have now retreated to one large base at the airport.
A final explosion may not be far away. Under article 140 of the new Iraqi constitution, there must be a vote by the end of 2007 to decide which regions will join the KRG. Mr Goran says that such a poll could see all of Mosul province east of the Tigris and the districts of Sinjar and Talafar to the west of the river joining the KRG. "As we get closer to the implementation of article 140, the problems will get worse," he says.
Patrick Cockburn is the author of 'The Occupation: War, resistance and daily life in Iraq' published by Verso.