He also said France's doctrine of nuclear deterrence has been extended to protect the country's "strategic supplies", taken to mean oil.

"Leaders of any state that uses terrorist means against us, as well as any that may be envisaging -- in one way or another -- using weapons of mass destruction, must understand that they would be exposing themselves to a firm and appropriate response on our behalf," he said.

"That response could be conventional, it could also be of another nature," Chirac said in a clear reference to nuclear weapons during a visit to a French nuclear base in the northwestern region of Brittany.