Barack Obama has not entirely lost his talent as an orator. Although, as Yossi Sarid put it in Haaretz, “his voice reveals frustration and disappointment in nearly every sentence”, his speech this week to the United Nations general assembly had many fine sentiments, well expressed.

But it was completely unable to hide the fact that America’s Middle East policy is headed for an almighty train wreck.

This year’s Arab Spring has been the biggest defeat ever suffered by al-Qaeda and its fellow extremists. It has shown that the path to change in the Middle East lies not through terror or fundamentalism but through popular protest. The Arab masses have demonstrated a willingness to risk their lives not for the hazy goal of a restored caliphate, but for very Western-style human rights and democracy — the ideals that the US, for all its faults, still represents.

What a triumph for America! But now, with its impending veto of the UN move for Palestinian statehood, the US is sending exactly the opposite message: that America stands against self-determination and in favour of military rule, that the path of negotiation and compromise goes nowhere, and that the extremists who said Obama would never be able to bring Israel to the table were right all along.

Jon Stewart’s words from last March were prophetic: “Offer not valid in West Bank or Gaza.”

And the disaster is a grimly inevitable one. It is simply unthinkable that Obama could do anything else. It’s a bald fact about the way American politics works that no president, and especially no Democrat, facing a difficult re-election campaign could possibly defy the Israeli government on such a high-profile issue.

Obama has Rick Perry breathing down his neck, who believes that support for Israel — by which he means support for the most right-wing elements in Israel, going even beyond Likud if necessary — is a religious duty for Christians. Any sane person in Obama’s position would feel justified in running almost any risk to prevent someone like that becoming president.

In 14 months, if he wins re-election, Obama may feel able to re-engage with the Middle East in a way that might promote peace and understanding. But by then it will quite probably be too late: a new Arab leadership may have turned its back on the very idea of co-operation with Israel or the US, and the region may descend into a new cycle of violence.

For now, Obama has basically given Benyamin Netanyahu everything he wants. Unfortunately that is the very reverse of what Israel needs. The refusal to contemplate serious engagement with the Palestinians is laying up dreadful troubles for the future; as Peter Beinart says in The Daily Beast, Netanyahu “has weakened two of the men Israel most needs to avoid becoming a global pariah”, namely Obama and Mahmoud Abbas.

So the Palestinian leadership — as moderate a leadership as Israel is ever likely to get — has been forced to try an alternative route, going to the UN to ask for what American policy, under Clinton and Bush as well as Obama, has long proclaimed as their right.

It’s Obama’s tragedy that he can’t possibly give it to them.