US and Iran lead clash of world views at UN assembly
The annual high-level meeting of the UN General Assembly is a place where US presidents have traditionally set out their world view, attempting to signal crucial shifts in Washington's international engagement.
This year was no different; with President Barack Obama eager to stress the continuing US commitment to spreading prosperity and democracy even at a time of austerity.
But this is a very different kind of democracy promotion to that of the George W Bush era, emphasising economic change; democratic reform that goes with the grain of individual societies, with America leading as much by force of example.
More pressing business though featured prominently in the president's remarks.
With Israel's deadline to end its partial moratorium on settlement building in the West Bank looming in a few days time, President Obama inevitably focused on the Middle East as the key diplomatic business of the moment.
He noted that the Israel-Palestinian peace process "had travelled a winding road over the last twelve months with", as he put it, "few peaks and many valleys".
But to the pessimists and the cynics who doubt that conditions are ripe for peace, he reaffirmed why he believes that there was simply no alternative to talks.
"If an agreement is not reached the hard realities of demography will take hold, and more blood will be shed," he said.
That reference to the "hard realities of demography" represents a clear warning to Israel to acknowledge that trends in the region are not in their favour and to act on the consequences.
He called for the moratorium on settlement construction to be extended.
There was advice too for those Arab states who back a comprehensive peace in the region. Mr Obama urged them to take tangible steps towards normalisation with Israel and to provide additional political and financial help for the Palestinian Authority.
"Those who want to see an independent Palestine rise," he said, "must stop trying to tear Israel down".
On Iran, President Obama struck a restrained but firm tone, insisting that "the door remains open to diplomacy should Iran choose to walk through it".
But, he said, "the Iranian government must demonstrate a clear and credible commitment, and confirm to the world the peaceful intent of its nuclear programme".
From the Iranian President Mahmoud Ahmadinejad there was an altogether different tone.
His speech was part political diatribe, part sermon; a wide-ranging presentation of his own particular world view.
He insisted that capitalism was collapsing and a whole new system of global governance was needed.
He said that the world should be run by virtuous people, like the divine prophets.
President Ahmadinejad took the consequences of the 9/11 attacks in New York and Washington as an example of what was wrong with the world, suggesting there were various interpretations of what happened, among them the possibility that the attacks were orchestrated by the United States itself to save what he called "the Zionist regime".
At this point the US delegation got up and walked out of the chamber.
They were followed by the representatives from some 33 other delegations; all the European Union countries, Canada, Australia, New Zealand and Costa Rica.
Walk-outs during the Iranian president's speeches are becoming a routine feature of diplomatic practice.
A US state department spokesman subsequently issued a short but blunt statement in response.
"Rather than representing the aspirations and goodwill of the Iranian people", Mark Kornblau said, "Mr Ahmadinejad has yet again chosen to spout vile conspiracy theories and anti-Semitic slurs that are as abhorrent and delusional as they are predictable."
Mr Ahmadinejad himself appeared undaunted. He continued with his scathing attack on Zionism and Israel.
On the nuclear front he gave little ground, insisting that nuclear energy was "a heavenly gift".
"Those who had used intimidation and sanctions against Iran," he said, "were destroying the remaining credibility of the United Nations."
Nonetheless he did say that Iran stood ready for a serious debate with US statesmen. However, there was little indication in this speech that they would have much to talk about.
Interestingly, speaking to a very senior White House official here in New York, it was clear that over the past year a number of senior Iranian figures have made approaches to the US administration eager to establish some kind of back-channel diplomacy.
However, the US view is that while it wants dialogue, it does not want to become entangled in factional battles in Tehran, preferring to wait until somebody with the approval of Iran's Supreme Leader takes the first step.