NEW YORK (AP) — Campaign politics shadowing every word, President Barack Obama on Tuesday will challenge the world to confront the root causes of rage exploding across the Muslim world, calling it a defining choice "between the forces that would drive us apart and the hopes we hold in common."

Obama will step before the United Nations General Assembly and declare that the United States will not shrink from its role in troubled, transitioning nations despite the killing of four Americans in Libya, including U.S. ambassador Chris Stevens, and more than 50 people total in violence linked at least in part to an anti-Muslim film.

Obama will also to seek to show U.S. resolve in preventing Iran from developing a nuclear weapon, a menacing issue that has undermined White House relations with Israel's leadership.

In his final international address before the November election, Obama will stand up for democratic values on a stage afforded to presidents, not presidential challengers. He will use it to try to boost his political standing without ever mentioning Republican opponent Mitt Romney.

Were there any doubt that the U.S. presidential campaign hung heavy over Obama's speech, Romney shredded it by assailing Obama's foreign affairs leadership on the eve of the president's speech. Now comes Obama's chance to assert his world vision on his terms.

"Today, we must affirm that our future will be determined by people like Chris Stevens, and not by his killers," Obama said of the U.S. ambassador, who was killed during an assault on the U.S. consulate in Benghazi, Libya, that the White House has deemed a terrorist attack. "Today, we must declare that this violence and intolerance has no place among our United Nations."

The White House released excerpts in advance of Obama's midmorning speech.

Obama's comments will be scrutinized around the globe and by the gathering of presidents and prime ministers in the famed United Nations hall, given the tumult, terrorism, nuclear threats and poverty that bind so many nations. His emphasis will be on the unrest in the Muslim world and on Iran, whose disputed nuclear ambitions have unnerved much of the world and caused tension between the United States and longstanding ally Israel over whether Obama has forcefully defined his breaking point for military action.

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"Make no mistake: a nuclear-armed Iran is not a challenge that can be contained," Obama says in his speech. He adds: "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."

That language remains as specific as Obama will publicly describe his "red line" for military intervention.

Setting a sharp political context for the speech, Romney went on the offensive Monday.

"This is time for a president who will shape events in the Middle East, not just be merciful or be at the mercy of the events," Romney said. Focusing on the killing of Stevens and mass bloodshed in Syria, Romney repeatedly ridiculed Obama's comment that nations moving toward democracy after the Arab Spring face "bumps in the road."

That prompted White House spokesman Jay Carney to fire back at Romney: "There is a certain rather desperate attempt to grasp at words and phrases here to find political advantage, and in this case that's profoundly offensive."

Obama's activities at the United Nations say plenty, too: There are not many of them. Campaigning is his imperative.

He is skipping the private meetings with key allies that a U.S. president typically schedules when the whole international community comes to New York. The president will spend only 24 hours in New York in total this time, and he spent some of it Monday to appear on "The View," giving a talk show interview intended to sell his election pitch to a big TV audience.

The dominant theme of Obama's U.N. speech will be his response to the protests raging in places across the Middle East and North Africa. As he has for days, Obama will condemn the violence, defend democratic principles of free speech and promise no U.S. withdrawal of outreach.

Much of the growing ire is aimed at the United States because of anti-Islam film produced in this country, but the White House has now deemed the attack on its consulate in Libya a "terrorist attack" and has not ruled out the possibility it was premeditated. Obama now says it "wasn't just a mob action."

"There are no words that excuse the killing of innocents," Obama says in the speech excerpts. "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."

In a preview of Obama's speech, Secretary of State Hillary Rodham Clinton appealed Monday for Muslims to show "dignity" as they protest the film denigrating the Prophet Muhammad.

"Dignity does not come from avenging insults," she said in a speech to her husband's Clinton Global Initiative. Romney and Obama were to speak there as well on Tuesday.

The secretary of state was also standing in for Obama, meeting with the presidents of Afghanistan, Egypt, Libya and Pakistan. She was due later in the week to meet with Israeli Prime Minister Benjamin Netanyahu and Palestinian leader Mahmoud Abbas.

For U.S. presidents, the yearly United Nations address is always laced with domestic politics even though the speeches are scripted without campaign references. Wars and the failed attempts at Mideast peace have dominated in recent years.

Romney's campaign made the campaign linkage directly Monday.

"On the eve of his United Nations address, President Obama's foreign policy is in disarray," spokesman Ryan Williams said. "As president, Mitt Romney will repair our relationships abroad and create a safer, more secure nation."

Polling shows Obama has a clear edge over Romney when voters are asked who they think is a stronger leader and would better protect the country.

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Associated Press writer Matthew Lee contributed to this story.

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