Iraq's biggest province has suffered a total breakdown in law and order in which al-Qaida has emerged as the dominant political force, according to descriptions of a classified US military intelligence review reported today.

The report, by the US marine corps colonel Peter Devlin, focuses on the vast, arid region of Anbar in the west, which contains the insurgent-held towns of Fallujah, Ramadi and Haditha.

The Washington Post quoted military officers who had seen the report as saying the area was "beyond repair".

"We haven't been defeated militarily, but we have been defeated politically - and that's where wars are won and lost," was one army officer's summary of the review quoted by the newspaper.

The same officer concluded that there were no functioning Iraqi institutions in the province, and that al-Qaida in Iraq, the insurgent group founded by Abu Musab al-Zarqawi, was Anbar's most powerful political force.

The report is believed to be the most negative one sent from the field in Iraq.

Mr Devlin has been stationed in Anbar since February and is regarded as one of the military's most respected and level-headed intelligence officers, adding to concern in Washington about his comments.

"In the analytical world, there is a real pall of gloom descending," the newspaper quoted the former defence analyst Jeffrey White as saying.

Four marines were killed in July in Anbar province, and nearly 22,000 marines are currently based in the region.