French Defence Minister Herve Morin and a NATO spokeswoman, meanwhile, insisted today there were no signs that French forces were hit by friendly fire in Tuesday's deadly attack.
Sarkozy has stressed his commitment to keeping French troops in Afghanistan, despite mounting political questions at home about the mission.
"We don't have the right to lose there," Sarkozy said at a solemn funeral ceremony for the 10 victims in the courtyard of the Invalides complex on Paris' Left Bank. "A defeat at that end of the world would be a defeat for French troops."
Sarkozy agreed in April to boost France's contingent by 700 troops to about 2,600, after the United States pressed NATO allies to shoulder more of the burden in the increasingly violent Afghanistan war.
Foreign Minister Bernard Kouchner reiterated that France was committed to staying the course in Afghanistan.
"I remind you that terrorism is winning," he told reporters after a government meeting Thursday. "Everyone knows that terrorism is particularly fed by what is happening in Afghanistan."
Sarkozy brushed off questions about whether French forces were hit by friendly fire in the ambush, insisting the day of the funeral was a moment for contemplation and mourning. But he said the incident would be fully investigated.
"I want (the families) to know everything, they have that right," Sarkozy said.
Survivors of the ambush were quoted in France's Le Monde newspaper as saying it took hours for backup to arrive when the troops were ambushed by insurgents. The report also said French troops were hit by friendly fire from NATO planes.
Morin and NATO denied the report, and Morin said reinforcement troops were sent to the scene within about 20 minutes of the ambush.
"No French soldier during the incident came on the radio to complain that they were taking friendly fire," NATO spokeswoman Carmen Romero said. "No French soldier after the incident has reported through the chain of command that might have been the case. None of the wounds sustained by those killed or wounded were consistent with air-delivered ordinance."
Morin told RTL radio that French fighters could not enlist F-15 jets sent to the scene "because the forces were very interlocked, the Taliban insurgents and the French forces. There would have of course been collateral damage if the bombs had been deployed."
Sarkozy and many government ministers attended Thursday's ecumenical funeral service in the Saint-Louis des Invalides church, solemnly approaching one by one the coffins draped with the French tricolor and topped with red berets.
Family members, mostly women and children, kissed the coffins, weeping and gripping each other for support.
The ceremony continued with Sarkozy's speech in the courtyard. The president made each of the killed servicemen a knight in the Legion of Honor, one of the nation's highest awards.
Tuesday's ambush was the deadliest for French forces in years.
