Barring President Mahmoud Ahmedinejad from Ground Zero or suggesting that he should be banned from speaking at Columbia University is the wrong way to deal with the threat posed by Iran’s nuclear ambitions. America’s plan for new sanctions imposed by a “coalition of the willing” should be a better one.

But in the week of the United Nations’s General Assembly, the US’s plan to go it alone, once again, with a few allies – notably Britain, France and Germany – is bound to seem like a rebuff to the principle of international cooperation.

It need not. The United Nations is not as stricken as its critics would have it, but Russia and China are so deeply divided from the West on some questions that agreement may be impossible; Iran, more than climate change, may be one of those. To justify tougher sanctions without the blessing of the UN Security Council, the US needs to show first that some sanctions are better than nothing, and secondly, that it is acting in the spirit of treaties against proliferation. It can do both, although its recent too-indulgent nuclear deal with India weakens its case.

From all the fuss, you would have thought that it was the first time that President Ahmedinejad had been to New York. But he has used the two UN General Assemblies since his June 2005 election to lay out his views on Iraq, Israel and the supposed injustice of depriving Iran of nuclear skills, with no obvious deference to the principle of cooperation in pursuit of peace.

The row this year has been provoked by his desire to broaden his appearances beyond the stage of the UN, with a request to visit the site of the twin towers, and to speak at Columbia. The refusal in the case of Ground Zero, and the uproar in both, is understandable but misplaced.

Those who opposed his plans believe that his views on Israel should disqualify him. There is no question that his government is malevolent towards Israel, most actively through funding Hezbollah. There is room for debate (although a tedious one) about whether he actually said it should be “wiped from the map”; his words are better rendered as “erased from the pages of history”, but first translations by Iranian news agencies appear the culprits in crafting the phrase for which he is famous. But should this bar him from Ground Zero? There are those who think that he is little different from Osama bin Laden, but that rhetoric blurs important distinctions: the Iranian regime’s loathing of al-Qaeda and the deep liking for the US among many ordinary Iranians. It is entirely possible that his request to visit the site was meant as a gesture of respect, although what it reveals is his naivety about the US and inability to predict its reactions.

And Columbia? An institution committed to freedom of speech is not endorsing his position by allowing him to state it. It is hard to argue that an audience of 600 gives more oxygen than the airwaves to which he has constant access.

The better questions are about the US’s new attempt to agree more sanctions by the West, outside the Security Council. The drive to get a deal through the council has been stalled by last month’s deal misguidedly offered to Iran by the IAEA, the UN nuclear watchdog. If Iran is sensible enough to do what the IAEA asks, no new sanctions proposal will get past Russia and China, who will argue that Iran is doing enough. Those who want more sanctions will have to impose them themselves.

That would not be not an assault on UN principles; it is fair to argue that it would support the Nuclear Non-Proliferation Treaty, one of the world’s most ambitious attempts at arms control. But it would lack the moral weight of a council-backed plan – and the practical force, too.

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