It is no mystery that US President Barack Obama and Israeli Prime Minister Benjamin Netanyahu are not each other’s first choices for their respective jobs.

Washington and Jerusalem have spent almost four years seeking to dismiss recurring news stories about the friction between these two men and, more importantly, their policies.

Whether or not these differences are media-hyped, they exist and are bound to become wider as the election season advances and Iran’s nuclear programme continues its march to weapons capability.

Recent utterances by US Chief of the US Joint Staffs General Martin Dempsey indicated again that America was not prepared to back Israel in what appears to be a looming pre-emptive strike against Iran’s nuclear installation. Fuelled also by leaked details of a stormy exchange between US ambassador to Israel Dan Shapiro and Mr Netanyahu, the air is filled with suspicion and recrimination.

Here, then, is what matters about Israel, Iran and the United States.

First, Israel will not attack unless it feels that the window for a successful military operation is closing.

Second, if Israel were to make this decision, US electoral circumstances would matter little — for Israeli leaders, this is a life-or-death decision which they are not likely to postpone over an electoral calendar.

Third, no US president would risk consigning his name to history as the one who let Iran go nuclear. President Obama is no exception and Republican candidate Mitt Romney’s accusation that he has “thrown Israel under a bus” would be proved false if it came to the crunch. If Mr Dempsey and his colleagues in US intelligence agencies told Mr Obama that Iran was about to cross a critical threshold, it is unlikely that the president would hold off a strike because of an election.

Fourth, given the historical precedent of intelligence failing to predict nuclear breakout in countries such as India, Pakistan, North Korea, Iraq, Syria and Libya, point number three is infinitely less reassuring than at first glance.

Fifth, for Israel, the threshold for a nuclear Iran comes much sooner than for the US. Point three, again, is moot to a large extent because, in all likelihood, the Americans are correct, from their perspective, when they say Iran is one to three years away from a nuclear bomb. Their threshold is weapons assembly, but for Israel and its more limited strike capabilities, crunch time comes sooner.

Sixth, brinkmanship on this matter comes to an abrupt end with the onset of the rainy season over Iranian skies — rhetoric is weatherproof, air raids are not — and might not wait until spring.

For Israel, letting the US electoral cycle come to fruition might mean postponing a decision until April 2013. By this time, it may be too late. For America, postponing until November 7 means ensuring that no foreign policy crises distract the president from a re-election bid in a very tough year.

Israel’s dilemma, then, will become more acute in the coming weeks: showing loyalty to a president Israel’s leaders do not fully trust may deprive it of its ability to steer the ship of history as it wishes. And that is not an option.

Emanuele Ottolenghi is a Senior Fellow at the Foundation for Defence of Democracies in Washington DC