And the other is highly political, namely that President Barack Obama might well be forced, against his better judgment, to back an Israeli strike in the heat of an election campaign.
One reason the outcome is so hard to predict are the many variables ahead. One is the region's increasing instability, especially on Israel's northern borders. If Syria were to transfer chemical weapons to Hizbollah, both Israel and the US have suggested they would intervene. Israel might find itself so embroiled in a war with Hizbollah that it would delay opening a second front against Iran.
On the other hand (and perhaps more likely) a war with Iran's proxies could rapidly expand into a confrontation with Tehran, including an Israeli attack on its nuclear facilities.
Another variable is whether Obama would, as Netanyahu would like, set a date by which the US would itself enact the military option unless Iran had agreed to halt its perceived march to a point where it could quickly build a bomb if it so decided.
Another possibility is that Obama supplies Israel with the deep penetration bombs it lacks in return for a delay which would allow more time for sanctions and diplomacy to work. But for now at least, Netanyahu is keeping the world guessing.
WILL ISRAEL LAUNCH ATTACK ON IRAN?
Yossi Alpher, former senior Mossad official and co-editor of the Bitter Lemons website: "It is clear that they [Benjamin Netanyahu and Ehud Barak] do not have the majority of the public behind them. The large majority of the security establishment is against them. The US is quite firmly against ... On the other hand, they believe in the necessity of doing it and they have been campaigning in recent weeks assiduously ... Factoring in all these elements, I come up with just under 50 per cent probability that this will happen as matters stand today."
Nazenin Ansarin, Iranian managing editor, Kayhan: "If three months ago [the chance of a strike ] was 70 per cent, now it is 80-85 per cent. The only way for the threat of war to decrease is a change of regime in Iran. Whether that takes place before war or after is the question."
Uri Dromi, spokesman of Rabin and Peres governments (1992-1996): "[Barak and Netanyahu]... seem to be moving towards a strike despite the advice of the military and the former head of Mossad ... As things stand I would put it at 60/40 in favour of a strike."
- Independent