Leading article: Hope for the best, prepare for the worst

There are many reasons to be sceptical about the assertion by the US Defence Secretary, Leon Panetta, that Israel is likely to attack Iran in the next few months.

For years, Israeli security officials have insisted to anyone who will listen that, without swift military action, Iran's path to a nuclear weapon is assured. Those claims have not so far been borne out. Iran, a recent International Atomic Energy Agency (IAEA) report says, has still not started to build a bomb.

But the calculus may be changing. The IAEA document contained irrefutable evidence of Iran's progress towards that goal. And the rhetoric on all sides has heated up. In Israel, report after report suggests that a growing portion of the military establishment believes an attack has to be launched soon. That conclusion, though, is based on a flawed analysis. It relies on the belief of Israel's defence minister, Ehud Barak, that Iran will soon enter an "immunity zone", where its work on a nuclear weapon is so far advanced that an attack would be powerless to reverse it.

Even if so catastrophic a course were necessary, however, Israel's estimate of when the window for action would expire extends to nine months. The US, with its greater military capability, would have more than a year. In the meantime, Iran's increasingly aggressive rhetoric is just one sign that sanctions are starting to bite. Diplomatic options are far from exhausted.

So why did Mr Panetta talk with such morbid confidence of an impending attack? He may have been speaking out of little more than frustration at Israel's continued reluctance to co-ordinate its military strategy with that of the US. But to date, the Obama administration has played its difficult hand steadily, and there is reason to hope that the defence secretary's remarks were carefully calibrated. Perhaps he intended to concentrate the relevant minds on making the sanctions regime work.

Unfortunately, things may not be so simple. Whatever Mr Panetta's intentions, the likelihood of an Israeli attack can really be known only to two men: Mr Barak and Israel's prime minister, Benjamin Netanyahu. And only a fool would exclude the possibility that their intentions, however ill-advised, are deadly serious.