The massacre of 16 Afghan villagers by an out-of-control US soldier will severely harm the current talks between Washington and Kabul on a long-term strategic pact which will start in 2014 when the present Nato mandate comes to an end. Anti-American feeling is very high indeed in Afghanistan, as this mass killing follows the burning of several copies of the Quran last month, and persistent killing of civilians by Nato troops over the years.

The Taliban have already promised that they will take revenge, which is likely to win much more popular appeal than President Hamid Karzai's feeble condemnation of the rampage as "intentional murders" and seeking an explanation from his American allies. The shocking incident will also harden anti-war opinion in Washington, taking into consideration the administration's failure to deliver on its war aims after spending billions of dollars and the loss of many lives on all sides.

The events of early Sunday morning are still becoming clear, but it seems that a single American staff sergeant left his base in the middle of the night and killed 16 civilians including nine children and three women. There was no provocation, nor any Taliban activity of any kind. This atrocious failure of control has to be dealt with properly.

This murderer should be tried by the Afghan courts, but if the Americans refuse to hand him over to Afghan justice, then it is important that their own courtmartial deals with the person with the full rigour of the law. It is very important that all soldiers know that they have to work within the law, and that they cannot be outside the law. A heinous crime has been committed and it has to be investigated and judged.