Israel is drawing up plans to attack Iran's nuclear facilities and is prepared to launch a strike without backing from the US, it has been reported.

Officials in the Israeli Defence Ministry told the Jerusalem Post that while they prefer to act in consultation with the US, they were preparing plans that would allow them to act in isolation.

"It is always better to coordinate," a senior Defence Ministry official told the newspaper. "But we are also preparing options that do not include coordination."

However defence officials played down the reports today, telling The Times that an attack by Israeli forces alone would probably fail to take out all of Iran’s nuclear facilities, which experts say are scattered across several sites, some deep underground.

“We could not risk an operation which would only partially succeed," one defence official told The Times.

"That would leave us open to a nuclear attack from Iran’s remaining weapons stock. Israel would likely need the support, the backing, of forces from a Western ally to successfully carry out the operation,” he said.

A senior Israeli official quotes in the Jerusalem Post said that while it would be difficult, it would not be impossible to launch a strike against Iran without permission from the US.

"There are a wide range of risks one takes when embarking on such an operation," a senior Israeli official was quoted as saying.

The US Airforce controls the Iraqi airspace Israel's jets would have to cross on a bombing mission and access to codes from the Americans, would “significantly improve” Israel’s chances of a successful strike on Iran, an official told The Times.

He added that because the Iranians have been moving the bunkers deep underground, sophisticated weaponry would be needed to successfully destroy the facilities.

Responding to reports that Israel would use low-yield nuclear “bunker-busters”, the official said the method was largely speculative and unreliable.

Ehud Olmert, the Israeli prime minister, has reportedly asked the US for a green light to attack Iranian facilities as recently as May.

According to Israeli officials, the US denied the request, although it outfitted Israel with the X-band radar system which would shave several crucial minutes off Israel’s reaction time to an Iranian missile launch, and allow the United States to oversee Israel’s airspace.

“There is always the option of Israel going it alone. It just does not seem like a good option at present time,” an Israeli MP told the Times.

There are three central locations where experts believe Iranian facilities are producing goods for nuclear weapons.

Israeli officials named these sites as: Natanz, where thousands of centrifuges produce enriched uranium; Isfahan, where 250 tons of gas are stores in tunnels; and Arak, where a heavy water reactor produces plutonium.

Israeli officials said they were heartened that international sanctions on Iran were having an effect, but did not feel they were enough to stop Tehran’s nuclear ambitions.

The most recent Israeli intelligence reports estimate that Iran will have enough enriched uranium for a nuclear weapon in late 2009, barring any interruptions in its programme.

"There is still time and there is no need to rush into an operation right now," another Israeli official said. "The regime there is already falling apart and will likely no longer be in power 10 years from now."

On Monday, Teheran dismissed the possibility of an Israeli strike, saying it didn't take Israel seriously.

"We think that regional and international developments and the complicated situation faced by Israel itself will not allow it to launch military strikes against other countries," Iranian Foreign Ministry spokesman Hassan Qashqavi told reporters in Teheran, adding that "Israel makes threats to promote its psychological and media warfare.

Some Israeli security officials fear that the Iranian retaliation for a strike on its facilities could include a large-scale missile attack on Israel from several Iranian allies, disruption of oil supplies to the West, and terror attacks against Jewish targets around the world.

Times Recommends

• 'Lost' cargo ship Arctic Sea gives up its secrets
• Army wants to retreat in Afghanistan
• Jungle angel was Obama’s mother