US President Barack Obama has promised that international forces will not "rush for the exits" in Afghanistan, after an American soldier was accused of murdering 16 civilians.
Mr Obama told US television stations that the troops must be withdrawn in a responsible way.
The killings in Kandahar province have strained relations between Afghans and foreign forces.
Afghan MPs passed a motion earlier saying Afghans had run out of patience.
The Taliban has promised revenge attacks. But a tribal elder told the BBC that he would not be calling for protests.
Anti-US sentiment is already high after soldiers burned some copies of the Koran at a Nato base in Kabul last month, sparking deadly riots across the country.
Mr Obama told local CBS station KDKA that the shooting was "absolutely heartbreaking and tragic".
When asked if the incident had made him think that the troop withdrawal should be quickened up, he said: "It makes me more determined to make sure we're getting our troops home."
He added: "What we don't want to do is to do it in a way that is just a rush for the exits."
Mr Obama said that international forces had to make sure the Afghans could secure their borders and stop al-Qaeda from getting back into the country.
Details about the shootings are still unclear, but the American soldier left his base in the southern province of Kandahar in the early hours of Sunday.
Witnesses said he tried the doors of several houses, and broke into three, shooting and killing anyone he found. Most of the dead were women and children.
The soldier later turned himself in to military authorities, and is in custody.
Pentagon officials said they would not release his name while the investigation was going on.
Reports said the soldier was in his 30s with three children.