For months now Israel has watched with alarm as its best friend has schmoozed its worst enemy.
The government of Benjamin Netanyahu has warned repeatedly that the United States should not take the overtures of the new Iranian President Hassan Rouhani at face value.
Its deepest fear has been that Iran will somehow sucker the world powers into relaxing the crippling regime of sanctions in return for concessions which merely slow down but do not stop the development of its nuclear capabilities.
Mr Netanyahu clearly thinks that point is being reached – or is in danger of being reached.
He went to Tel Aviv airport to meet the US Secretary of State John Kerry – who was passing through on the latest stage in a round of Middle East shuttle diplomacy – and on the way in offered a gloomy assessment of the state of play.
“I understand that the Iranians are walking around very satisfied in Geneva as well they should be,” he said. “They got everything and paid nothing. Iran got the deal of the century, and the international community got a very bad deal.”
It wasn’t just the words either, gloomy as they were.
Mr Netanyahu radiated disapproval and disappointment.
Ronen Polak, diplomatic correspondent for Israel’s Channel One TV, tweeted from the scene that the Israeli prime minister was as angry and sullen as he had seen him in years, adding that US officials had cancelled a scheduled photo opportunity.
The implication of that was perhaps that the gulf between American optimism about a possible breakthrough with Iran and Mr Netanyahu’s suspicion that the US and its allies are being duped would not have made for a very good photograph.
To some extent a thaw between Iran and the global alliance negotiating over its nuclear capabilities is a personal blow for the Israeli prime minister, who has made it a personal mission to warn the world of the dangers he sees emanating from Tehran. It has been one of his favourite themes for 20 years now.
He devoted his recent speech at the United Nations to the issue and feels the rest of the world has been to quick to react to a change of tone from Tehran and has not been firm enough in demanding changes of substance.
In his school of thought there are two dangers in an Iranian nuclear weapon.
The first and most obvious is that the current leadership – or some future regime – might be tempted to use the weapons to carry out the old threat to “wipe Israel off the map”. That existential threat has to be taken seriously, of course.
But, goes this argument, there’s a second and much broader risk too, and that is that Iran intends to use the bomb not just to establish itself as a regional superpower but also to change the global balance of power between the Islamic and non-Islamic world. Rightly or wrongly the possession of nuclear weapons edges you closer to a seat at the high table of world politics.
Israel has not historically found itself with many allies on nuclear issues in the Middle East.
It evades questions about its own nuclear arsenal with what it calls a policy of “nuclear ambiguity” but that doesn’t cut much ice in the Arab world – or in Iran – where its universally assumed that Israel has the bomb.
But it is far from alone in worrying about Iranian nuclear ambitions.
As the leader of Shia Islam, Iran is locked in a long-term battle for strategic supremacy with its Sunni rival, Saudi Arabia.
They are already fighting a vicious proxy war in Syria but the nuclear sphere would provide an even more dangerous arena for competition.
Saudi Arabia is almost certainly as worried about Iranian nuclear ambitions as Israel but it doesn’t say as much in public.
That is probably partly because it does not want to appear to be so clearly on the same side of a public row as Israel and partly because its simply not the kingdom’s style.
The two countries have something else in common as well – they are historically close strategic allies of the United States and share an irritation with Washington’s sudden openness to Tehran which they are cautious about expressing in public.
Not everyone in Israel shares these fears over Iran to the same extent as Benjamin Netanyahu of course, but he appears to see himself in the role of a prophet on the matter – although with relations between Iran the rest of the world apparently thawing he feels for the moment like a prophet crying out in the wilderness.
It is hard to say what will happen next.
The Western world has been applying sanctions to Iran for around 30 years so it has a choice of older restrictions which it could lift without disturbing the much more effective measures its taken more recently which have hit Iran’s energy and financial services sectors. If that is the strategy then some Israelis might feel they could live with it.
But Mr Netanyahu has said that Israel is committed to making sure that Tehran never gets a nuclear weapon – and there are plenty of people in think tanks around the world who will now begin speculating again about the possibility that the Israeli government might begin contemplating some kind of pre-emptive campaign of air strikes to make sure it does not happen.