Leaked portions of an International Atomic Energy Agency (IAEA) report scheduled for release tomorrow indicate that Iran's nuclear program is closer to a weapon than previously suspected by the watchdog.

In the run-up to the release there's been plenty of breathless speculation about whether Israel is planing to take matters into their own hands and bomb Iran. Yesterday, Israeli President Shimon Peres called Iran "the greatest danger, both for Israel and for the entire world." There's been a furious Israeli public debate over a possible air attack on Iranian nuclear facilities for the past week, and US officials have been sending up smoke signals that they're worried about it.

The Russians have been more direct. Foreign Minister Sergei Lavrov said today that an air strike "would be a very serious mistake fraught with unpredictable consequences."

So, are we nearing some kind of military showdown, with Israel in the lead? Probably not.

Israel's fear of a nuclear Iran is deeply felt, and shouldn't be ignored. But an operation to take out Iran's nuclear program – widely dispersed, in a country far from Israeli air space – would be fraught with risks, and is precisely something Iran's military planners have been preparing for since at least 1981, when Israel took out Iraq's nuclear program in one surprise strike. Israel could certainly delay Iran's nuclear program, but is unlikely to destroy it.

And the aftermath of an attack could see renewed fighting with Lebanon's Hezbollah, which might take up the banner of "resistance" in Iran's name and rain shells on northern Israel. The chances of counteraction from Hamas-controlled Gaza is also real, though less of a direct military threat.

Finally, the stance of regional neighbors and foreign partners also contain risks. While most Arab governments would be delighted to be rid of the risk of an Iranian nuclear program, their people might not agree. A flurry of propaganda is all but guaranteed in the wake of an Israeli strike – claims that schools or civilians, not bona fide weapons facilities were hit, whatever actually happened. Given the context of greater calls for political change in the region after the ousters of Tunisia, Egypt and Libya's dictators, Israel's diplomatic isolation in the region is likely to grow.

Farther away, the US relationship with Israel could be complicated. Though the US is withdrawing from Iraq by the end of the year, large numbers of US soldiers will remain in harms way in Afghanistan, which shares a border with Iran, and the chances that Iran might encourage local proxies into greater attacks on US troops can't be discounted.

In other words, the risks are high, success is difficult, and whatever hope there may be that the Iranian regime will respond to diplomatic pressure by changing course will evaporate in the wake of a strike. On that basis, it's hard to see Israel making a rational decision to act. That moment, if it ever comes, will probably be driven by the development of an actual Iranian nuclear bomb, and evidence that Iran has the capacity to deliver it to an Israeli city.

Warnings of an imminent Israeli attack on Iran have, for years, come and gone with the seasons. In August 2010, Atlantic writer Jeffrey Goldberg wrote that in his opinion there was a "greater than 50 percent chance" that Israel would attack Iran by July of 2011. His article attracted a flurry of attention and debate. As it happened, as with all such predictions in the past, the attack didn't happen.

I think the likelihood of unilateral Israeli action is about as low now as I though it was then. If the articles on the looming IAEA report are true – that it argues Iran has developed the knowledge to build a bomb – it will be alarming, and will add to the risk of an eventual military confrontation. But diplomacy, talk of sanctions, cajoling and threat will grind on much longer before arms are taken up.

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