Leading article: With each day, the threat of civil war is growing

It was unfortunate timing for our Foreign Secretary that the destruction of the Golden Mosque at Samarra came only hours after he had flown to Baghdad with a personal appeal to Iraq's politicians to co-operate on a government of national unity. Jack Straw may have a case to answer, among other things, for allowing the influence of the Foreign Office to decline; for his over-optimism about Iran, for the occasional inarticulate presentation of British policy on early morning radio - but the terrible events of yesterday served only to highlight the utter impotence of outsiders (even British cabinet ministers) to save Iraqis from themselves. There might have been a time when strings tugged sharply by the occupiers could have had some effect. The bombing of the Shia shrine at Samarra, and its bloody aftermath across Iraq, showed that this time - if it existed - is over. With ever fewer vulnerable foreign civilians to target, the insurgents have turned on other Iraqis.

Now we have seen the first flash of the civil, sectarian, war that was always feared. According to one recent "worst case" scenario, the real sectarian violence would break out only if foreign forces left too soon. The evidence from the shattered dome at Samarra, and the violent response to it, is that it could break out a great deal sooner. Armed clashes have been reported between Sunni and Shia from Baghdad to Basra.

Not for the first time, we are contemplating the all too predictable consequences of a reckless invasion and the hopelessly mismanaged occupation that followed. Incentives for Iraqis to persist with the status quo are dwindling. It was disclosed this week that, even by the most basic material indicators, Iraq is now worse off than it was under Saddam Hussein.

Oil production, after an initial increase, is now lower than it was then. The same goes for supplies of clean water and electricity - the measure by which many ordinary Iraqis judge their wellbeing. We hardly need mention security. Those same opinion surveys which suggested that a majority of Iraqis thought the benefits of ousting Saddam outweighed the disadvantages have now swung the other way.

Meanwhile, the options narrow by the day - for the occupying powers as for the flailing Iraqi authorities. Each set of elections was supposed to give Iraqis a say in their future, restore the country's sovereignty and foster stability. The hope was that the country would attain something akin to representational democracy. Each time, Iraqis voted peacefully in large numbers, but always along ethnic and religious lines.

The parliamentary elections last month left Iraq with a parliament dominated by Shias, but with an insufficient majority to form a government. Talks on a coalition are proceeding painfully slowly. The prospects for a central administration that will carry more conviction than its predecessor look remote.

It is still possible that, even at this late stage, the threat of a bloodbath could be averted. While the firebrand cleric Muqtada al-Sadr brought his militants on to the streets and vowed to "defend the Iraqi people" if the government did not do so, the Shia leader, Grand Ayatollah Ali al-Sistani, appealed to his followers to keep their protests peaceful. The President, a Kurd, and government ministers united in calls on Muslims to close ranks against violence.

The coming days will be as crucial as any Iraq has lived through since the invasion. The government's national security adviser, a Shia, insisted yesterday that the insurgents would fail to draw the Iraqi people into civil war "as they have failed in the past". We only wish we could be as certain.