Obama Vows to Keep Iran from Nuclear Weapon

President Barack Obama will tell the United Nations Tuesday that the United States will "do what we must" to prevent Iran from getting a nuclear weapon, according to excerpts from his speech.

He also planned to address the Middle East turmoil sparked by an offensive anti-Islam Internet video and the killing of the U.S. ambassador to Libya in a wide-ranging speech just six weeks before the November 6 U.S. election.

"Make no mistake: a nuclear-armed Iran is not a challenge that can be contained. It would threaten the elimination of Israel, the security of Gulf nations, and the stability of the global economy," Obama was to tell the U.N. General Assembly, according to speech excerpts released by the White House.

"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."

Obama also planned to address the deadly protests that erupted across the Middle East in response to an amateurish American-made Internet video 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 U.S. envoy 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."

Six weeks ahead of the presidential election, Obama has faced a barrage of criticism from Republican rival Mitt Romney over his handling of the protests.

The White House insisted ahead of the U.N. address that it would not be a campaign speech, but the event will allow Obama to wield the power of an incumbent to present his foreign policy platform on a world stage.

Obama will spend only a day in New York -- without the normal meetings with world leaders -- before heading back to the campaign trail.

Romney on Monday accused Obama -- who had spoken of "bumps in the road" following the Arab Spring uprisings -- of minimizing the murder of the four Americans in Benghazi in the attack two weeks ago.

"When the president was speaking about bumps in the road he was talking about the developments in the Middle East, and that includes an assassination," Romney told NBC News.

"It includes a Muslim Brotherhood individual becoming president of Egypt, it includes Syria being in tumult, it includes Iran being on the cusp of having nuclear capability, it includes Pakistan being in commotion."

Obama polls well on foreign policy, but the Democratic narrative -- anchored to the killing of Osama bin Laden and the withdrawal from Iraq -- has been complicated by the violent protests of the last two weeks.