President Obama: Shooting of 16 Afghan civilians 'heartbreaking'
President Barack Obama has called the shooting of 16 Afghan civilians by an American soldier "heartbreaking".
But he says it makes him more determined to get US troops home after more than a decade in Afghanistan.
However he has insisted that the killings will not affect US strategy or the timing of the withdrawal.
The BBC's world affairs editor John Simpson reports.
12 Mar 2012