France threatened to withdraw early from Afghanistan after an Afghan soldier killed four French troops and wounded 15, in a setback for the US-led coalition's efforts to build a national army and allow foreign troops to go home.
The shooting - the second against French forces in a month - is the latest in a rising number of disturbing attacks in which Afghan security forces or infiltrators have turned their guns on coalition forces.
It came during an especially deadly 24 hours for the international coalition, with six US marines killed in a helicopter crash on Thursday night in southern Afghanistan.
French president Nicolas Sarkozy, who faces a potentially tough re-election campaign this spring, reacted swiftly and sternly to the killing of the French troops, who were unarmed when they were shot during a physical training exercise.
He ordered French forces to stop training Afghan forces and suspended joint patrols.
"The French army is not in Afghanistan so that Afghan soldiers can shoot at them," Mr Sarkozy said in Paris. "From now on, all the operations of training and combat help by the French army are suspended."
If security for the French troops is not restored, "the question of an early withdrawal of the French army would arise", he said.
France's threat comes at a time when the coalition is trying to reassure Afghanistan that it is not rushing to leave, that it will continue to develop the nation's struggling security force, and that it will help the government negotiate a political settlement with the Taliban to end the decade-long war.
If France suspends training operations indefinitely or withdraws sooner, it would weaken the coalition and could prompt more troop-contributing nations to follow suit.
Through training of Afghan police and soldiers, the coalition hopes to wrap up its combat mission at the end of 2014 when foreign forces are to have gone home or moved into support roles.