By James Robbins
BBC Diplomatic Correspondent
The leading foreign policy think-tank, Chatham House, is warning that Iraq faces the distinct possibility of collapse and fragmentation.
Four years since the invasion, violence in Iraq is unrelenting
A new report from the London-based Chatham House, also known as the Royal Institute of International Affairs, argues that the Iraqi government is now largely powerless and irrelevant in large parts of the country, as a range of local civil wars and insurgencies are fought.
The report urges a radical change in American and British strategy to try to rescue the situation.
It is not the first time Chatham House - a highly respected foreign policy institution in London - has been highly critical of American and British strategies in Iraq.
This latest paper, written by Dr Gareth Stansfield, a Middle East expert, is unremittingly bleak.
Dr Stansfield, of Exeter University and Chatham House, argues that the break-up of Iraq is becoming increasingly likely.
In large parts of the country, the Iraqi government is powerless, he says, as rival factions struggle for local supremacy.
The briefing paper, entitled Accepting Realities in Iraq, argues that "There is not 'a' civil war in Iraq, but many civil wars and insurgencies involving a number of communities and organizations struggling for power."
Dr Stansfield says that, although al-Qaeda is challenged in some areas by local Iraqi leaders who do not welcome such intervention, there is a clear momentum behind its activity.
Iraq's neighbours too have a greater capacity to affect the situation on the ground than either the UK or the US.
The report accuses each of Iraq's major neighbouring states - Iran, Saudi Arabia and Turkey - of having reasons "for seeing the instability there continue, and each uses different methods to influence developments".
The briefing paper says "these current harsh realities need to be accepted if new strategies are to have any chance of preventing the failure and collapse of Iraq".
Need for change
Dr Stansfield contends that the American security surge is moving violence to different areas, but is not overcoming it.
Certainly there is a growing sense in London and Washington that the American Commander in Iraq, General Petraeus, is likely to ask for more time to continue the surge later this summer in order to deliver results.
That will confront the Bush Administration with a real dilemma.
The president has vetoed a bill that would have set a deadline for the withdrawal of US troops from Iraq.
The bill was approved by both the House of Representatives and the Senate.
Congressional opponents of the war believe the veto signals that now it is the president alone who must take responsibility for continuing America's involvement, and the casualties.
The report urges the governments in London and Washington to change track.
It says the radical cleric Moqtada Sadr, leader of the Mehdi army (one of the major Shia militias), should be included as a political partner - no longer treating him as an enemy.
And it also calls for increasing the involvement of other countries in the region.