French President Jacques Chirac for the first time on Thursday raised the threat of a nuclear strike on any state that launches "terrorist" attacks against France.
He also said France's doctrine of nuclear deterrence was 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.
Chirac said he was extending the definition of "vital interests" protected by France's nuclear umbrella to include allies and "strategic supplies."
The French press understood "strategic supplies" to include oil. Le Monde newspaper said that was aimed "probably also at those countries from which France imports part of its energy needs."
"If, theoretically, such interests were threatened by regional powers -- Iran, North Korea? -- France would react," the daily said.
Chirac, however, did not single out any country in his speech.
He did indicate, though, that the previous Cold War stance of threatening massive and widespread destruction against enemies had been changed to a doctrine permitting a graduated and limited nuclear response.
"Faced with a regional power, our choice is not between doing nothing and annihilating it," he said.
France has configured its nuclear arsenal to be able to respond "flexibly and reactively" to any threat by reducing the number of nuclear heads on certain missiles on board its submarines, he said.
Such a move would enable it to conduct strikes on specific targets and limit the zone of destruction.
"It would be up to the president of the republic to evaluate the potential magnitude and consequences of unacceptable threats or blackmail against our interests," he said.
Such a situation could lead a French head of state to declare those "vital interests," he said.
Chirac said "the fight against terrorism is obviously one of our priorities," but he added that "it is not because a new threat appears that it causes all the others to disappear."
"Our world is marked by the emergence of affirmations of power that rely on the possession of nuclear, biological or chemical weapons," he said.
In an apparent reference to Iran, Chirac condemned "the temptation by certain countries to obtain nuclear capabilities in contravention of treaties."