President Francois Hollande has said that his country would intensify fight by air strikes against Islamic State (IS) militants in Syria and Iraq.
Speaking in Paris after talks with UK PM David Cameron, Mr Hollande confirmed French aircraft carrier Charles de Gaulle would join the military action.
It comes as the Belgian capital, Brussels, remains on the highest level of terror alert for a third day.
Suspected Paris attacks gunman Salah Abdeslam remains at large.
The two leaders agreed to step up co-operation on countering international terrorism, including increased data-sharing and sharing of airline records.
The Islamic State group has said it was responsible for the Paris attacks, in which 130 people were killed.
“I firmly support the decisive action taken by President Hollande to strike Isil [IS] in Syria, it is my firm belief that we should do so too,” Mr Cameron said in a statement at a news conference.
Mr Hollande said: “We will intensify our strikes, choosing targets that will do the most damage possible to this army of terrorists.”