President Sarkozy has pledged France's continued commitment to Afghanistan after visiting French troops and meeting President Hamid Karzai, BBC reported.
He was speaking in Kabul after French troops suffered some of their worst casualties in recent times.
Ten French soldiers were killed and 21 injured in an ambush by Taleban fighters east of the capital, Kabul.
Mr Sarkozy said France was committed to the fight against terrorism, and the mission in Afghanistan would continue.
"Even though the toll is so high, you should be proud of what you are doing. The work that you're doing here is indispensable," Mr Sarkozy told his troops.
"We're going to make sure that the means are put in place to ensure that this doesn't happen again." France has 2,600 troops serving in Afghanistan.
The 10 deaths brought to 24 the number of French troops killed in Afghanistan since 2002, the AFP news agency reports.
There was more violence on Afghanistan on Wednesday. A bomb went off in a busy market in the south-eastern province of Khost.
Officials say that in addition about 19 Taleban fighters were killed in two separate clashes in Khost and in the province of Paktia.