Leading article: A war that will haunt Mr Blair until he departs

There can be no doubting, either, the Prime Minister's commitment to Iraq's future. He regards the formation of the unity government as the last piece of the constitutional jigsaw, which in formal terms it is. Outwardly, the components are in place for Iraqis to govern themselves. Pointing out that Iraq now had a government of national unity in which all major groups were represented, Mr Blair said sharply that there was "no vestige of excuse for anyone to carry on with terrorism or bloodshed". Which is where Mr Blair's vision of Iraq as he would like it to be parts company with the harsh reality that the military intervention has brought about. During the few hours that the Prime Minister was in Baghdad, more than 40 Iraqis were reported killed or injured. That most of the casualties are now Iraqis reflects the change in the character of the conflict from the first year of the occupation, but it does not make it any less destructive for Iraqis.

Mr Blair's only allusion to this disconnect was his rather wistful statement that the transition to a "new beginning" had been "longer and harder than any of us would have wanted it to be". That is putting it very mildly. Regrettably, the transition is neither complete, nor guaranteed to be successful.

Despite more than five months of haggling, key government posts remain vacant. An incomplete cabinet, though, is the least of Iraq's difficulties. The uncomfortable truth is that institution-building has its limits. Iraqis may have voted many times, but this does not mean that they have a functioning or lasting democracy. They have an institutional shell into which they may, with forceful and visionary leadership, be able to breathe life - but this cannot be taken for granted.

The lack of security hampers everything. If attacks on foreign troops have fallen, it is because they have adapted their tactics to reduce opportunity to a minimum. But sectarian violence has grown exponentially, and it is not at all clear when, or whether, it will cease. Parts of the country are in the grip of ethnic cleansing. And where once there were informal armed bands, there are now organised militias.

The militias are one by-product of three years of disorder, but only one. Supplies of water and electricity are less reliable than they were under Saddam Hussein. Oil production is far below levels envisaged by the US at the time of the invasion; it is depleted further by corruption and theft. Without security, these problems will continue; and unless they are solved there will be no security. Iraq's new government is in a double bind.

Mr Blair's own double bind relates to the presence of British troops, which remains part of the explanation for his poor poll ratings at home. "It is the violence that keeps us here," he said in Baghdad, "it is the peace that allows us to go." But peace remains elusive, even in the Shia south. The hope expressed yesterday was that responsibility for security in most of Iraq will be handed over to Iraqis by the end of this year. If so, some troops will come home. The expectation, it also emerged yesterday, however, is that British troops will remain until 2010. Responsibility for Iraq will burden Mr Blair until his last days in office.