Western countries, led by the U.S., suspect the Islamic republic of harboring ambitions to produce a nuclear weapon.
"There is nothing more dangerous than the situation in Iran. This region is extremely perilous - this is the world's most dangerous place. If an Iranian bomb is added to this, then it would be very difficult in my opinion," Bernard Kouchner told Europe 1 radio.
He reiterated that the worst-case scenario was war.
Kouchner provoked anger in the Islamic Republic in an interview broadcast on French TV and radio on September 16, saying that if Tehran develops an atom bomb, "We must prepare ourselves for the worst," and adding that "The worst means war." However, he later said his statement had been wrongly interpreted by journalists.
Iran has denied any intentions to develop nuclear weapons, saying its nuclear program is transparent and civilian-oriented. The country recently intensified its cooperation with the UN nuclear watchdog.
The U.S. House of Representatives approved on September 25 a bill toughening sanctions against Iran, and banning the White House from any new nuclear cooperation with Russia and other countries cooperating with the Islamic Republic in the nuclear sphere.
The draft law also envisions that the largest branch of the country's military, the Islamic Revolutionary Guard Corps (IRGC), could be put on the list of terrorist organizations.