"Terrorism will not succeed in fracturing our national community," he said in a TV address as police in Toulouse tried to negotiate the surrender of a self-declared Islamist militant holed up in a flat after a series of killings.
"I say to the entire nation that we must be united," Sarkozy said after meeting with Muslim and Jewish leaders in the Elysee palace to discuss community relations in the wake of the deadly gun attacks.
The president said that the French should not be tempted by revenge and should understand that the attacks had nothing to do with religion.
Officials named the suspected killer as Mohammed Merah, a 24-year-old French citizen of Algerian origin who has bragged of being an Al-Qaeda member and claimed to have acted to avenge the deaths of Palestinian children.
He is suspected of gunning down three off-duty soldiers, three Jewish children and a rabbi in three separate attacks.