UNITED NATIONS (AFP) — President Barack Obama warned yesterday that the United States would “do what we must” to prevent Iran from getting nuclear weapons, in a declaration to be given to the UN General Assembly.

Advance excerpts from a speech the US leader was to give on the first day of the United Nations summit showed he was also to address the protests that swept the Muslim world this month in response to an anti-Islam Internet video.

Just six weeks before he is due to seek re-election, Obama is under pressure on the foreign policy front, with criticism of his handling of the killing of US diplomats and claims he is not standing closely enough behind Israel.

His speech will attempt to answer those critics and reassure the world leaders gathered in New York that he is determined to face down Iran.

“Make no mistake: a nuclear-armed Iran is not a challenge that can be contained,” he was to declare, according to the advance remarks.

“It would threaten the elimination of Israel, the security of Gulf nations, and the stability of the global economy.

“That is why a coalition of countries is holding the Iranian government accountable. And that is why the United States will do what we must to prevent Iran from obtaining a nuclear weapon.”

Iranian leader President Mahmoud Ahmadinejad was also in New York preparing for his own annual UN speech and was in typically defiant form, denying that Iran is seeking the bomb and dismissing threats of military action.

Aside from Iran, the civil war in Syria was also due to dominate the agenda.

UN leader Ban Ki-moon, France’s President Francois Hollande and Qatar’s emir, Sheikh Hamad bin Khalifa Al-Thani, a key backer of the Syrian opposition, were expected to lambaste Syrian President Bashar al-Assad on the opening morning.

The diplomatic assault will go on all week as Arab and European leaders vent their outrage after UN-Arab League envoy Lakhdar Brahimi warned Monday that the conflict is worsening with no immediate hope of ending the war.

Brahimi accused Assad of using “medieval forms of torture” on opponents.

The Islamist occupation of northern Mali, conflict in eastern Democratic Republic of Congo and Somalia’s attempts to build a new state out of the ruins of war will also be raised.

Obama also planned to address the deadly protests that erupted across the Middle East in response to an amateurish Internet video made by American Christian extremists that insulted the prophet Mohammed.

“Today, we must affirm that our future will be determined by people like Chris Stevens, and not by his killers,” he says, referring to the US ambassador killed with three other Americans in an attack on the Benghazi consulate.

“Today, we must declare that this violence and intolerance has no place among our United Nations. There are no words that excuse the killing of innocents. There is no video that justifies an attack on an embassy.

“There is no slander that provides an excuse for people to burn a restaurant in Lebanon, or destroy a school in Tunis, or cause death and destruction in Pakistan.”

The White House insisted ahead of the UN address that it would not be a campaign speech, but the event will allow Obama to respond to criticism of his foreign policy from his Republican challenger Mitt Romney.

Romney accuses Obama of playing down the murder of the four Americans in Benghazi and of failing to recognise the threat posed by the rise of Muslim Brotherhood in Egypt, the civil war in Syria and Iran’s nuclear quest.

The General Assembly is to carry on through the weekend and into Monday, but the highpoints were to be the leaders’ speeches yesterday and today.