For America, it's all about timing. Can Israel afford it?
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Beyond the speech atmospherics of the Aipac conference where, in rapid succession, Israel's president Shimon Peres, US President Barack Obama, Israel's Prime Minister Benjamin Netanyahu and US Secretary of Defence Leon Panetta all spoke at length about Iran, the constant of the game remains the same. Israel and America agree that a nuclear Iran is unacceptable. The devil is in the details, for the two allies seem to continue to disagree on the timetable of an Iranian nuclear weapon.
For US decision-makers, it is not clear that Iran has made the strategic decision to assemble and test a nuclear weapon, regardless of how soon Iran may be capable of actually doing so. Besides, due to different military capabilities, Israel's timetable is considerably shorter than America's.
Iran has begun to shift its enrichment activities to a heavily fortified underground facility under a mountain near the Shi'a holy city of Qom. Those facilities are deemed impenetrable from an air attack conducted by Israel and, if all Iran's enriched uranium stockpiles were moved there, Iran would be immune from an Israeli air attack - though not from an American one.
For Israel, there is comfort in strategic convergence on US and Israeli threat assessments. Regardless, the two allies do not see eye to eye - especially given that the US has the luxury of more time thanks to its military might and its ability to inflict enduring damage on Iran's nuclear programme even after its leaders have put it out of reach of Israel's air force.
America is Israel's most precious ally. No Israeli leader would jettison such an alliance lightly. Bet on Netanyahu then to do his utmost to push Israel's patience to the outer limits of Iran's nuclear ticking clock - he will wait until five, maybe even one, minute to midnight.
But these words, uttered by an Israeli premier, can only mean one thing. Israel will not let Iran cross the line where Iran remains in the run for nuclear weapons and Israel has to rely on others for "the fate of our very survival".
Emanuele Ottolenghi is a Senior Fellow at the Foundation for Defence of Democracies