French Prime Minister Bernard Cazeneuve on Thursday warned troops stationed in Africa's Sahel region that they should "prepare for a long war" against Islamist militants.
He also promised Chad, where French troops have been stationed since 2014 under Operation Barkhane, his nation's financial support.
"Our country must continue to make clear and ambitious budgetary decisions in support of our armies," Cazeneuve said on his first overseas visit as prime minister.
The Barkhane forces' mission is to target Islamist militant groups that are active in the Sahel region south of the Sahara Desert.
The operation was launched after French military interventions in Mali and Chad.
"We must prepare for a long war in an environment that has undergone dramatic shifts," Cazeneuve said.
The French military is currently battling Islamist militant in two regions -- in the Middle East against the Islamic State (IS) militants, and in the Sahel where it has deployed 4,000 soldiers as part of the Barkhane force.
Operation Barkhane covers five nations: Mauritania, Mali, Niger, Burkina Faso and Chad.
Cazeneuve hailed troops fighting on fronts "thousands of kilometres away from their homes".
"You risk your lives to save others'," he said.
Four French troops have been killed in Mali this year.
Barkhane forces are working alongside Malian troops in the search for Sophie Petronin, a French aid worker who was kidnapped last weekend.
The prime minister also pledged France's help for poverty-stricken Chad.
"France will always help Chad surmount its difficulties," said Cazeneuve after a meeting with President Idriss Deby.
Like its neighbour, oil giant Nigeria, Chad has been undergoing a severe financial crisis as a result of a several months-long slump in the price of crude.
While the world's major oil producers have agreed to cut back on production in order to bring prices back up, the impact of the change remains to be seen in the worst-affected nations.
The opposition in Chad is also critical of the political situation under Deby's iron-fisted rule.