Mahmoud Ahmadinejad, the Iranian president, has launched a stinging attack at the United Nations on the US and other major powers as militarist, imperialist and unfit to dominate global governance.
Ahmadinejad's verbal assault on the west and Israel promoted walkouts by diplomatic delegations. US diplomats were the first to leave, when Ahmadinejad referred to the "mysterious September 11 incident" as a pretext to attack Afghanistan and Iraq.
Later, he criticised the US for killing Osama bin Laden and burying his body at sea, saying the al-Qaida leader should have been brought to trial.
Other delegations, including those from the UK and France, walked out later when the Iranian leader said that if European countries were still paying a "fine or ransom to the Zionists" because of the Holocaust, they should also pay reparations for slavery.
In other parts of his speech he spoke of Zionists being responsible for "mass murder and terror against the Palestinians", and said the US and west "view Zionism as a sacred notion and ideology". The Israeli delegation had decided not to attend.
Ahmadinejad, apparently in an attempt to strengthen his political position in Iran, dedicated much of what is likely to be judged as one of his most controversial speeches to asking rhetorical questions about who was responsible for slavery, colonialism and wars over the generations.
He also asked which countries' economies relied on military spending; who provoked Saddam Hussein to attack Iran; and "who used the atomic bomb against defenceless people?"
Ahmadinejad accused Nato of occupying Afghanistan and of sanctioning drug trafficking, claiming that narcotics production has risen since the US-led invasion a decade ago.
Later, he accused the US and its allies of targeting Iran, which is under sanction over its nuclear programme, because it has challenged orthodoxy. "By using their imperialistic media network which is under the influence of colonialism, they threaten anyone who questions the Holocaust and the September 11 event with sanctions and military actions," he said.
The Iranian leader said this made the US and its allies unfit to dominate the international system, and called for change to the structure of the UN security council.
But he made no direct reference to the issue that has dominated diplomatic wrangling in New York this week – the Palestinian request for statehood to the security council.
The Palestinian leader, Mahmoud Abbas, is expected to lay out his case for going to the security council in a speech to the UN on Friday, while insisting it is not meant as an alternative to negotiations. Abbas is also expected to say that the move is not a threat to Israel.
That is not how the Israeli prime minister, Binyamin Netanyahu, sees it. He may use his speech, later in the day on Friday, to repeat his assertion that the security council move is destabilising, could result in false expectations and violence, and undermines the negotiating process.
The tone of the two leaders' speeches will be set in part by Barack Obama's address on Wednesday, which was strongly praised by Israel but has been met with widespread criticism among UN delegations, many of whom regard it as a piece of electioneering as the US president seeks to defuse Republican criticism that he has not backed Israel strongly enough.
Critics said the tone of the American president's remarks, and his failure to speak directly about occupation or mention the continued construction of Jewish settlements, added weight to a call by the French president, Nicolas Sarkozy, for an end to US domination of mediation in the conflict.
Abbas is expected to submit the request to the security council after his speech, but the Palestinians have backed away from pressing for an immediate vote, under intense pressure – particularly from Europe – to avoid forcing the US to carry out a threat to veto the move and to give a breathing space to try and relaunch peace negotiations.
The Palestinians also have reason to pause, because it is not certain that they have enough votes to win in the security council whether or not the US vetoes the request. Abbas needs the support of nine of the 15 members, but not all have publicly declared their position.
Some of those thought to be sympathetic to the Palestinian position – notably Bosnia and Gabon – are under intense pressure from the US to abstain.
However, while Netanyahu received strong backing from the White House, the Israeli prime minister was warned by his predecessor, Ehud Olmert, that he is facing his last chance to make peace, and he should not be wasting political capital opposing the Palestinian request to the security council.
"As tensions grow, I cannot but feel that we in the region are on the verge of missing an opportunity – one that we cannot afford to miss," Olmert wrote in an article for the New York Times.
"The Israeli prime minister, Benjamin Netanyahu, has declared publicly that he believes in the two-state solution, but he is expending all of his political effort to block Mr Abbas's bid for statehood by rallying domestic support and appealing to other countries. This is not the wisest step Mr Netanyahu can take."
Olmert said the Arab spring is changing the political dynamic in the Middle East, and that it is important for Israel to cement existing peace agreements with Egypt and Jordan, as well as reaching a deal with the Palestinians.
"We Israelis simply do not have the luxury of spending more time postponing a solution. A further delay will only help extremists on both sides who seek to sabotage any prospect of a peaceful, negotiated two-state solution," Olmert said.
