There was a sigh of disappointment around the world when news broke on Tuesday that the presidents of the USA and Iran were not going to shake hands. The White House had encouraged speculation that Barack Obama might chance upon Hassan Rouhani in the corridors of the UN. Journalists eager to add drama to the annual dronefest at the UN General Assembly picked up the ball and ran with it.
In fact, it was never likely that the two men would press the flesh after more than 30 years of estrangement. The Iranians never gave a hint that this was part of the plan, and any sober assessment of the balance of forces in Tehran would conclude that such a rash step would not help Mr Rouhani consolidate his power.
Despite the hype, the divide between Iran and America is not something that can be crossed with expressions of peace and love. Handshakes, in any case, are more appropriate when the diplomatic deal is sealed rather than as an empty sign of goodwill.
Mr Rouhani's speech, while stripped of the provocations of his predecessor, Mahmoud Ahmadinejad, was hardly a surrender document. He spoke of a somewhat limited "framework to manage our differences", making clear that the Islamic Republic still opposed America's global hegemony.
For his part Mr Obama was a touch more accommodating, stating clearly that he was not aiming at regime change, and referring to the fatwa of the supreme leader, Ayatollah Ali Khamenei, which renounced nuclear weapons. But he was not so indulgent as to avoid mentioning all the Americans who had been killed or taken hostage by Iran and its surrogates.
In short, neither side has yet made any substantive new step to unblock the impasse of the negotiations over Iran’s nuclear programme. For that reason alone, a handshake would have been premature.
The effect of all the handshake hype has been to open Mr Rouhani to accusations of being a simple PR man tasked to lift the sanctions which are strangling the Iranian economy.
This line of attack has been avidly pursued by the Israeli embassy in Washington and will be followed up when Prime Minister Benjamin Netanyahu delivers his UN speech warning the Americans against the mullahs’ “honey trap”.
Mr Rouhani is of course not the decider in the nuclear issue.
That role undoubtedly belongs to Ayatollah Khamenei, with the Revolutionary Guards jealously in control of the technology and viewing Mr Rouhani's election with deep suspicion.
By the same token, it could be said that Mr Obama is hardly the sole decider in this matter in America.
Just about the only thing that a divided Congress can agree on is rejection of Iran’s nuclear enrichment programme, which happens to be the Israeli line.
Mr Obama should still pursue negotiations. This is a rare opportunity. A chance to improve relations with Iran under the moderate president, Mohammad Khatami, was lost through American hesitation. It was killed stone dead when George W Bush, for the sake of a good line in his 2002 State of the Union Speech, included Iran in the “axis of evil”. So it should not be missed again.
But no one has indicated how the nuclear negotiation is going to work. Both sides will demand that the other moves first. Iran will demand that the US starts by easing the sanctions; Washington will open by saying that Iran must stop nuclear enrichment, as the UN Security Council has repeatedly demanded. Mr Rouhani told the UN that enrichment was Iran’s right and not a topic for discussion.
This is not like Richard Nixon going to China in 1972 to end 25 years of estrangement.
Both countries had a clear interest in doing so, though Washington needed all Henry Kissinger’s skills to get round the issue of the American ally Taiwan. But the Taiwan issue is nothing compared to the weight of Israel in America’s calculations in the Middle East, and the fears of its Arab allies at the prospect of growing Iranian influence in the region.
The prospects for a quick nuclear deal look cloudy. But what if Iran’s goal is a long-term change in how it is perceived in the region? For the mullahs to stay in power, Iran’s identity must remain based on opposition to America, but this does not require daily provocations against the US, particularly at a time when US power is waning.
Ray Takeyh, an Iranian-American scholar at the Council for Foreign Relations in New York, has suggested that Iran now wants to present itself as a force for stability in the region. By lining up with the US on the need for Syria to remove its chemical weapons, Iran has taken a step in this direction. This is in stark contrast to Moscow, which is clutching at conspiracy theories to try to shift blame from the Syrian regime for the August chemical weapons attack.
Iran is critical to US attempts to stabilise what the US calls the Greater Middle East. It could be helpful to the US in Afghanistan as the Pentagon moves its troops out next year. The chaos of Iraq is now forgotten in Washington, thanks to the ability of powerful countries to move on from their mistakes. But Iran is now the dominant outside power there and closer US-Iranian ties would surely benefit that country.
In the long term a more cooperative Iran might be seen as less of a threat to its neighbours. The world might then find its nuclear programme less threatening. It might be able to accept that Iran could have the technology but stop short of possessing nuclear arms, which would leave the tattered nuclear Non-Proliferation Treaty still just about credible.
That is a long way off. So far we have only a mullah’s smile, which is not a bankable currency. And certainly not one which is accepted by America’s allies or by Congress in Washington. But if, after 34 years of self-isolation, the Iranian regime wants to change the way the world sees it, then now is the time.
On Twitter: @aphilps