"It’s very simple: no civilian nuclear programme can explain Iran’s nuclear programme," he told France 2 television in an interview, two days after Tehran confirmed it was resuming sensitive uranium enrichment work.
"Therefore it’s a clandestine military nuclear programme."
The exact nature of Iran’s nuclear ambitions — Tehran insists that it just wants to make civilian nuclear power — has sparked an international standoff which has led to the brink of UN Security Council intervention.
Earlier this month the United States and a European Union troika made up of Britain, France and Germany persuaded the watchdog International Atomic Energy Agency (IAEA) to report Iran to the Security Council for action.
The world body is awaiting a March 6 report by IAEA chief Mohamed ElBaradei before deciding how to proceed.
"Firstly, the international community has sent a very strong message to the Iranians: show reason, suspend all nuclear activities and uranium enrichment," Douste-Blazy said, adding: "And they’re not listening to us.
"That is the reason why, for the first time for days, the international community is united. It’s not just the Europeans — France, Germany and the British — it’s also Russia and China."