Israel has drawn up secret plans to destroy Iran's uranium enrichment facilities with tactical nuclear weapons. Two Israeli air force squadrons are training to blow up an Iranian facility using low-yield nuclear bunker-busters", according to several Israeli military sources. The attack would be the first with nuclear weapons since 1945, when the United States dropped atomic bombs on Hiroshima and Nagasaki. The Israeli weapons would each have a force equivalent to one-fifteenth of the Hiroshima bomb. Under the plans, conventional laser-guided bombs would open "tunnels" into the targets. "Mini-nukes" would then immediately be fired into a plant at Natanz, exploding deep underground to reduce the risk of radioactive fallout. "As soon as the green light is given, it will be one mission, one strike and the Iranian nuclear project will be demolished," said one of the sources. Israeli and American officials have met several times to consider military action. Military analysts said the disclosure of the plans could be intended to put pressure on Tehran to halt enrichment, cajole America into action or soften up world opinion in advance of an Israeli attack. Some analysts warned that Iranian retaliation for such a strike could range from disruption of oil supplies to the West to terrorist attacks against Jewish targets around the world. Robert Gates, the new US defence secretary, has described military action against Iran as a "last resort", leading Israeli officials to conclude that it will be left to them to strike.