Curious things are going on in the Middle East. On the one hand, Israel seems to be taking some early, tentative steps towards peace with its nearest enemies. It has just agreed a six-month ceasefire with Hamas in Gaza; it is deep into indirect peace talks with Syria, aimed at a comprehensive treaty; and earlier this month came word that Israel is keen to have direct negotiations with Lebanon.

Yet all these welcome murmurings of peace are fighting to be heard above a growing drumbeat for war - against the country Israel fears more than any of its immediate neighbours: Iran.

Last week it emerged that no fewer than a hundred Israeli fighter planes had taken part in an exercise in the Mediterranean that looked uncannily like a practice run for an attack on Iran. Earlier the former defence minister Shaul Mofaz, who still sits in Israel's security cabinet, announced that "attacking Iran, in order to stop its nuclear plans, will be unavoidable".

And now, increasing the temperature another couple of degrees, comes the claim, reported in today's Guardian, that the Syrian site bombed by Israel last September was in fact a joint nuclear venture between Syria, North Korea and Iran. The defence analyst Shmuel Bar, who sits on Israel's national security council, is unambiguous: "It is 100% certain that the Iranians are on track towards a nuclear weapon and 100% certain that no diplomatic pressure will prevent it."

The Israelis believe this danger is more imminent than anyone else realises. They estimate the Iranians will pass "the point of no return" no later than 2010. They are utterly dismissive of sanctions. Bar asks what possible basket of carrots would persuade the Iranians to give up the benefits that would come from acquiring the bomb: "It would become the hegemon of the region, it would dictate oil prices, it would lead the Muslim world. Against all that, what can you offer?"

All this has apparently led Israel to conclude that it must act, alone if necessary. It harbours no delusions that it could take out the Iranian nuclear programme from the sky, as it did when it bombed Iraq's Osirak reactor in 1981, but it reckons its airforce could do enough damage to "set back" the Iranian nuclear effort for a year or two or more.

What to make of all this warlike talk? The simplest option is to take it at face value, to conclude that Israel is indeed going to act and is preparing the ground, militarily and politically. It wants its planes ready and also its arguments, so that if action is timetabled for "summer-fall 2008" as one Israeli analyst wrote this week, then it has at least made some effort to brace world opinion for the shock.

This view - that Israel might really mean it - rests on understanding what, for Israel's policymakers and public alike, are a series of givens. First, even though no one doubts that Israel itself is a nuclear power, it still carries a mortal fear of even a single Iranian bomb. That's because it believes the old cold war rules of nuclear balance and mutually assured destruction don't necessarily apply in its neighbourhood. Israelis recall the words of the former Iranian president Hashemi Rafsanjani, who in 2001 declared that "the use of a single atomic bomb has the power to destroy Israel completely, while it will only cause partial damage to the Islamic world". They took that to mean that Iran is big enough to withstand a nuke, while Israel is so small it would be wiped out with just one bomb. What's more, Israelis worry that a regime with a strong doctrinal belief in martyrdom might not fear national suicide the way that, say, the Soviet Union once did.

It does not help that Iran's current president regularly conjures up the threat of annihilation. There was some dispute over the precise meaning of Mahmoud Ahmadinejad's notorious warning that Israel would be wiped off the map, but, as if to avoid any confusion, he repeated the threat earlier this month when he proclaimed that Israel "is about to die and will soon be erased from the geographical scene".

In seminar rooms in London or Paris, it's easy to hear all this as mere metaphor, not to be taken seriously. But Israelis hear it differently. "We have a Holocaust complex," says David Landau, the former editor of Ha'aretz. Having faced a real attempt at total eradication in living memory it's quite understandable, he says, if Jews feel especially anxious when a sworn enemy starts threatening obliteration. Nor does it help that the Iranian president targets this most neuralgic spot, repeatedly questioning the historic truth of the Holocaust.

The result is that Israelis do not assess risk and probability like other states. It may not be an iron certainty that Iran wants to acquire a nuclear bomb that it will then hold over Israel's head - but if there is so much as a risk, says Landau, that is too much to live with.

After 2003, those watching from afar become sceptical when they hear doomsday talk of weapons of mass destruction - especially after December's US national intelligence estimate said the Iranian nuclear quest had been on hold for four years. Indeed, western intelligence agencies are said to be wary of sounding the alarm these days, chastened by their Iraq error. But the experience that haunts Israeli intelligence was the opposite, its underestimate of the threat in 1973 that led to the Yom Kippur war. It's underplaying a danger, not overplaying it, that Israel's military establishment now seeks to avoid.

There is an alternative way to read the current situation. It would see all the latest, apparently bellicose, moves as goads by the Israelis to spur the rest of the world into action: "Act now," they are saying, "because if you don't, we might just do something crazy."

That warning is surely worth taking seriously, if only because the consequences of military action against Iran are awful to contemplate. Iran would unleash a fierce retaliation, with American soldiers in next-door Iraq the first target. Tehran could choke the world's oil supply through the Gulf, then use its enormous influence not only to destabilise Iraq but to dispatch its proxies around the world on a campaign of attacks on civilian targets, with Hamas and Hizbullah forming the first wave. The head of the UN nuclear watchdog, Mohammed ElBaradei, has warned that a military strike would turn the region into a "ball of fire".

A world anxious to avoid that outcome either has to bet that, when it comes to it, Israel will duck confrontation and learn to live with a nuclear Iran - or it must find another way to prevent Tehran getting a bomb. Despite Israel's avowed scepticism, that can only mean diplomacy and the sanctions process.

One British official admits that the current effort is "only scratching the surface". The west has shut off access to the dollar, the pound and the euro - but it barely hurts the Iranians, who are awash in cash thanks to the soaring price of oil.

What's needed are sharper sticks and juicier carrots, including tolerance for an Iranian role in neighbouring Iraq and Afghanistan. The current western posture - no talks until Iran suspends its nuclear effort - surely cannot hold: Iran loses nothing by carrying on its quest. Tehran is not yet being forced to make a tough choice. It has to and soon - before Israel makes an even tougher one.

freedland@theguardian.com