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.

The plans, disclosed to The Sunday Times last week, have been prompted in part by the Israeli intelligence service Mossad’s assessment that Iran is on the verge of producing enough enriched uranium to make nuclear weapons within two years.

Israeli military commanders believe conventional strikes may no longer be enough to annihilate increasingly well-defended enrichment facilities. Several have been built beneath at least 70ft of concrete and rock. However, the nuclear-tipped bunker-busters would be used only if a conventional attack was ruled out and if the United States declined to intervene, senior sources said.

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.

Israel has identified three prime targets south of Tehran which are believed to be involved in Iran’s nuclear programme:

·  Natanz, where thousands of centrifuges are being installed for uranium enrichment

·  A uranium conversion facility near Isfahan where, according to a statement by an Iranian vice-president last week, 250 tons of gas for the enrichment process have been stored in tunnels

·  A heavy water reactor at Arak, which may in future produce enough plutonium for a bomb

Israeli officials believe that destroying all three sites would delay Iran’s nuclear programme indefinitely and prevent them from having to live in fear of a “second Holocaust”.

The Israeli government has warned repeatedly that it will never allow nuclear weapons to be made in Iran, whose president, Mahmoud Ahmadinejad, has declared that “Israel must be wiped off the map”.

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.

Israeli pilots have flown to Gibraltar in recent weeks to train for the 2,000-mile round trip to the Iranian targets. Three possible routes have been mapped out, including one over Turkey.

Air force squadrons based at Hatzerim in the Negev desert and Tel Nof, south of Tel Aviv, have trained to use Israel’s tactical nuclear weapons on the mission. The preparations have been overseen by Major General Eliezer Shkedi, commander of the Israeli air force.

Sources close to the Pentagon said the United States was highly unlikely to give approval for tactical nuclear weapons to be used. One source said Israel would have to seek approval “after the event”, as it did when it crippled Iraq’s nuclear reactor at Osirak with airstrikes in 1981.

Scientists have calculated that although contamination from the bunker-busters could be limited, tons of radioactive uranium compounds would be released.

The Israelis believe that Iran’s retaliation would be constrained by fear of a second strike if it were to launch its Shehab-3 ballistic missiles at Israel.

However, American experts warned of repercussions, including widespread protests that could destabilise parts of the Islamic world friendly to the West.

Colonel Sam Gardiner, a Pentagon adviser, said Iran could try to close the Strait of Hormuz, the route for 20% of the world’s oil.

Some sources in Washington said they doubted if Israel would have the nerve to attack Iran. However, Dr Ephraim Sneh, the deputy Israeli defence minister, said last month: “The time is approaching when Israel and the international community will have to decide whether to take military action against Iran.”