When’s the right time to punch your annoying next-door neighbour in the face?
It’s a slightly flippant analogy but it does sum up the dilemma that the Israeli military and political establishment feel they are facing regarding Tehran’s nuclear programme.
“If you have a big sword over your head, when does it become urgent? When it’s being built? Or when it’s five inches away or three or one inch away?”
This from a key figure involved in the planning for a possible future assault on Iran. He’s one of several people I’ve met privately over recent weeks at the very top of Israel’s political and military establishment.
Their thoughts, along with senior figures in Hamas, Hezbollah and diplomats and government officials from around the region and beyond, are the sources for this piece. All of them spoke candidly because it was off the record.
Israel considers Iran to be the “centre of gravity” influencing the flow of events stretching from Gaza to Afghanistan. And it is pushing hard the idea that the tide of opinion is now flowing Israel’s way.
A senior figure in the government told me that Washington is starting to use the language the Israelis were using 15 months ago.
For now Israel wants to be seen to be giving every opportunity for sanctions to provide a peaceful resolution.
What Israel would of course prefer is an American-led Nato mission to target all parts of the nuclear operation and wipe it out once and for all.
The US wouldn’t do that unless it felt that Iran was on the verge of going nuclear and that going nuclear wasn’t containable.
It’s hard to overstate just how preoccupied the leadership here is with the possibility of Iran obtaining a nuclear weapon. For them it’s about a tangible threat to their existence.
Eventually Israel might feel it has to go it alone even though it doesn’t have the capacity to finish the job by itself.
So it will focus its attack, if it comes, on five or six bottlenecks in the Iranian nuclear programme. If this puts back the programme five years or so, the Israeli leaders I’ve spoken to said it would be worth the trouble.
Easy to say, but going after Iran is a big gamble for a much smaller country. And it could easily stoke a much wider Middle East war.
The only thing that isn’t getting much airing during the debate here is, well, what if the Iranians are telling the truth.
I was in Baghdad for much of the run-up to and for the US-led invasion of Iraq. The arguments people made for bombing Iraq then sound eerily similar to those for bombing Iran now. And the arguments for bombing Iraq then turned out to be worthless.
The Americans say the Iranians are not being open and honest about their nuclear programme.
Say that in parts of the Arab world and they’ll ask why that standard isn’t being applied to the only country in the Middle East that almost certainly does have nuclear weapons – Israel.
The other issue that could widen a conflict is what Israel does about Iran’s so-called proxy, Hezbollah.
The suggestion is it would pre-emptively attack Hezbollah missile positions across the border in Lebanon too, fearing that Iran would try to use the militant group as its first mechanism for response.
Some Arab nations would happily watch Iran humbled but be furious about an attack on Lebanon.
The delicate balance for Israel is that Hezbollah know they may be a target if tensions rise and trouble with Iran looks imminent. Would Hezbollah sit around waiting to be hit or strike first?
To cut it short, a perceived failure in the new sanctions regime could speed up the prospect of serious trouble in the region.
Everyone agrees that Hezbollah has managed, since the July War of 2006, to diversify its armoury. There’s been much more argument over whether that includes the dreaded Scuds.
Syrians I spoke to said no, the Israeli military said yes, a member of the Israeli government said: “Well, one, maybe two.”
Militarily a big cumbersome Scud might not actually be that useful for Hezbollah but psychologically nothing touches the nerve of the Israeli population more.
Many of them still remember scrambling around for their gas masks when the Scud was the weapon of choice of Saddam Hussein in the first Gulf War.
Another factor that complicates things is that the White House doesn’t seem to like the Israeli government very much these days.
Someone very senior in the Israeli government put it to me like this: “I know the American people support us but I’m not sure about the White House. In Europe, I know the leaders support us – I’m not sure about the people.”
And that’s not hard to understand when you think that the Israeli government doesn’t even like itself much these days. Israel’s messy coalition politics gives horse-trading a bad name.
So the country has in Avigdor Lieberman a foreign minister who not only doesn’t support government foreign policy; he at times won’t even return the calls of the Prime Minister, Benjamin Netanyahu.
The next six months could be crucial to building a new coalition of the willing to deal with Iran and at the centre of this new coalition is an Israeli government that can barely stand the sight of each other.
“OK, look, I don’t like his style [and] it does do us some harm when dealing with the West… but he’s not an extremist.”
Hardly a ringing endorsement of Mr Lieberman from one of his close colleagues.
War and peace
And if his colleagues don’t like him much the Arab world hates him, which is probably why he has lasted so long in the job. But it doesn’t bode well for breathing life into a peace process.
America doesn’t want to see Iran get a nuclear weapon, but it also doesn’t want to bomb or approve the bombing of yet another Muslim nation without being seen to try to sort out the biggest gaping wound in the Middle East, the Palestinian issue.
President Obama wants to say the morning after Israel bombs bits of Iran to pieces: “At least we’re making progress on this one.”
And do Israel’s Western allies think this is an Israeli government committed to the peace process? I asked a senior diplomat very familiar with this region that very question recently and he said “No”.
So do we get a peace deal before we get another war? No, probably not.
But is America going to throw its weight, prestige and trust behind the present Israeli government when it comes to dealing with Iran. Again, probably not.
Taking on Iran could be a very messy business. Elements of the present Israeli government can’t stand the Obama administration and the feeling is mutual.
And no politician wants to go to war if the guy who’s “got your back” also has a history of sticking a knife into it.
This is the first in an occasional series of pieces by the BBC’s Middle East bureau editor based on off-the-record briefings by officials and decisions makers in the region.BBC