Admiral Mike Mullen, the chairman of the US Joint Chiefs of Staff, said he had seen nothing in the report that might lead to disciplinary action over the incident.

The incident, in Farah province in Afghanistan, caused serious tensions between the US and Afghan governments and the US has come under increasing criticism over the past year for civilian deaths during operations against Taliban and al-Qaeda fighters in Afghanistan and Pakistan.

Barack Obama, the US president, and other Washington officials have repeatedly expressed regret for civilian casualties and vowed to take measures that would avoid future attacks.

Report recommendations

The US is to send thousands more troops
to Afghanistan [Reuters]

The report, details of which had already been leaked to the US media, urges increased training for US troops.

It is also set to urge a review of the use of air support when targeting Taliban fighters after mounting civilian casualties that have provoked outrage in Afghanistan.

It recommends that US forces sent to Afghanistan should receive training in the kinds of scenarios they could face, including situations that have resulted in civilian deaths, one official told the Associated Press news agency.

And periodic refresher training throughout soldiers' tours of duty in the war zone was also set to be recommended by the report.

Death toll confusion

The review said the early May air raids were carried out against Taliban targets in Farah but that in at least one case it was unclear whether civilians were in the vicinity.

If the Afghan claims over casualties were confirmed it would make the incident the most deadly military operation involving civilians since the 2001 US-led invasion.

Preliminary US estimates had put the civilian death toll at between 20 and 35 and the number of Taliban fighters killed at 80 to 95.

An Afghan rights watchdog also said that 97 civilians died, and that no more than two Taliban fighters were killed, in addition to Afghan officials' claims of 140 dead.

The incident sparked angry protests in Afghanistan, with Afghans expressing outrage at the civilian deaths.