JERUSALEM (Reuters) - Ballistic missiles could be Israel’s weapon of choice against Iranian nuclear facilities if it decides on a pre-emptive attack and deems air strikes too risky, according to a report by a Washington think-tank.

An interior view of the Arak heavy water production facility in central Iran in a file photo. REUTERS/Fars News

Israel is widely assumed to have Jericho missiles capable of hitting Iran with an accuracy of a few dozen meters (yards) from target. Such a capability would be free of warplanes’ main drawbacks -- limits on fuel and ordnance, and perils to pilots.

Extrapolating from analyst assessments that the most advanced Jerichos carry 750 kg (1,650 lb) conventional warheads, Abdullah Toukan of the Center for Strategic and International Studies said 42 missiles would be enough to “severely damage or demolish” Iran’s core nuclear sites at Natanz, Esfahan and Arak.

“If the Jericho III is fully developed and its accuracy is quite high then this scenario could look much more feasible than using combat aircraft,” he said in the March 14 report, titled “Study on a Possible Israeli Strike on Iran’s Nuclear Development Facilities.”

Israel, whose jets bombed Iraq’s nuclear reactor in 1981 and mounted a similar sortie over Syria in 2007, has hinted that it could forcibly deny Iran the means to make an atomic bomb.

But many experts believe the Iranian sites are too distant, dispersed and protected for Israel’s warplanes to take on alone.

Israel neither confirms nor denies having Jerichos, as part of an “ambiguity” policy veiling its own assumed atomic arsenal.

Sam Gardiner, a retired U.S. air force colonel who runs war games for various government agencies in Washington, cast doubt on the usefulness of ballistic missiles against Iran, noting, for example, the robust fortification at Natanz.

This, he said, would required that attackers “burrow” into the targets using multiple, precision-guided bombs dropped by plane: “The American conclusion is that the only way to get deep enough is to put a second warhead into the hole of the first.”

Loath to see further destabilization of a combustible region, the Obama administration has championed engaging Iran diplomatically. Some U.S. officials have signaled unhappiness at the idea of Israel going it alone against its arch-foe.

REPRISALS

Toukan, whose 114-page report frowns on the prospect of unilateral Israeli action, said a Jericho salvo could draw an Iranian counter-attack with Shehab missiles. Other reprisal scenarios include Iran choking off oil exports, hitting U.S. Gulf assets, or ordering proxy attacks on Jewish targets abroad.

Some Israeli experts have been dismissive of the Shehab threat, citing intelligence assessments that Iran has deployed fewer than 100 of the missiles and that, if fired, most would be destroyed in mid-flight by Israel’s Arrow II interceptor.

“Under such circumstances, we would expect little more than a repeat of the Gulf war,” said one ex-general, referring to Iraq’s firing of 40 Scud missiles at Israel during the 1991 conflict. Those attacks inflicted damage but few casualties.

The Arrow II also provides some protection for Jordan, an Arab neighbor of Israel and which Toukan saw becoming “Ground Zero if a ballistic missile exchange takes place.”

He noted that any Jericho strikes on Iran -- which has denied seeking nuclear weapons but vowed to retaliate if attacked -- would be complicated should Tehran obtain the most sophisticated version of Russia’s S-300 air-defense system, which can tackle ballistic missiles as well as invading planes.

Israel could face a further difficulty in mounting a sneak Jericho attack because its strategic air bases are located near population centers. The unannounced test launch of what was believed to be a Jericho III outside Tel Aviv last year became public knowledge within minutes.

But that may be the extent of Iran’s forewarning. According to an Israeli defense consultant, only the United States and Russia have put up satellites capable of spotting ballistic missile launches in real time, “and it’s highly unlikely that the Iranians would get access to that information.”

The consultant, who spoke to Reuters on condition of anonymity, played down the notion of ballistic missiles being used for conventional attacks:

“You look at any major Western military, and you’ll see that such strikes are the purview of manned warplanes, while ballistic missiles are reserved for nuclear-strike scenarios.”