President Barack Obama addressed on Tuesday an anti-Islam film that set violence raging across the Arab world, while vowing that the United States would “do what we must” to prevent Iran from acquiring nukes.

Taking the podium at the United Nations six weeks before the U.S. presidential election, Obama sought to counter criticism of his foreign record by Republican rival Mitt Romney, who has accused him of mishandling the Arab Spring uprisings, damaging ties with Israel and not being tough enough on Iran.

Obama also challenged world leaders to stand united against anti-American violence that has swept many Muslim countries in recent weeks and to promote tolerance amid anger over a crudely made video that offended Islam. “There are no words that excuse the killing of innocents,” he said.

The President told the Assembly the United States had “nothing to do with the crude” anti-Islam film which mocked Prophet Mohammed and ignited deadly anti-American protests across the Muslim world.

“Let us remember that Muslims have suffered the most at the hands of extremism … Slander of Prophet of Islam should be condemned just as desecrated churches are and the denial of Holocaust is,” Obama said.

President Barack Obama Tuesday vowed to hunt those behind the “attack on America” in Libya that killed U.S. ambassador Chris Stevens two weeks ago and said a “disgusting” film that insulted Muslims was no excuse for violence.

“The attacks on our civilians in Benghazi were attacks on America. There should be no doubt that we will be relentless in tracking down the killers and bringing them to justice,” Obama said.

“Chris Stevens legacy will live on,” he added.

“Today, we must affirm that our future will be determined by people like Chris Stevens, and not by his killers. Today, we must declare that this violence and intolerance has no place among our United Nations.”

In his annual speech to the world body, Obama again condemned the video produced by Coptic Christian extremists in the United States that set violence raging across the Arab world as “crude and disgusting.”

But he said that however vile, no exercise of free speech that is protected by the U.S. Constitution could justify killing and violence.

“Here in the United States, countless publications provoke offense. Like me, the majority of Americans are Christian, and yet we do not ban blasphemy against our most sacred beliefs.

“Moreover, as president of our country, and commander-in-chief of our military, I accept that people are going to call me awful things every day, and I will always defend their right to do so.”

Obama also warned that in 2012 “when anyone with a cell phone can spread offensive views around the world with the click of a button, the notion that we can control the flow of information is obsolete.”

“The question, then, is how we respond. And on this we must agree: there is no speech that justifies mindless violence.”

“There are no words that excuse the killing of innocents. There is no video that justifies an attack on an embassy.”

He also stressed there has been “progress” since the Arab Spring but said the recent turmoil in the Muslim world showed the hard task of achieving true democracy.

“The events of the last two weeks speak to the need for all of us to address honestly the tensions between the West and an Arab World moving to democracy,” he said in the speech to world leaders.
Nuclear Iran ‘cannot be contained’

Seeking to step up pressure on Iran, Obama told the U.N. General Assembly that there is still time for a diplomacy but that “time is not unlimited.”

His tough talk appeared aimed at easing Israeli concerns about U.S. resolve to curb Tehran’s nuclear drive, as he reasserted before the world body that he would never let Iran develop an atomic bomb and then simply contain the problem.

But he stopped short of meeting Israeli Prime Minister Benjamin Netanyahu’s demand to set a specific “red line” that Iran must not cross if it is to avoid military action, and did not go much farther in his rhetoric than previously.

“A nuclear-armed Iran is not a challenge that can be contained,” he said. “It would threaten the elimination of Israel, the security of Gulf nations and the stability of the global economy.”

“The United States will do what we must to prevent Iran from obtaining a nuclear weapon.”

U.S. officials have repeatedly said that all options are on the table against Iran – code for a possible military strike – while Israel’s Netanyahu has called for a U.S. ultimatum to Iran. But Obama did not repeat that line in his speech.
Syria sanctions

Meanwhile, Obama said Iran “propped up a dictator in Damascus,” in reference to Syrian leader Bashar al-Assad and his Tehran ally.

On the Syrian conflict, Obama said there must be “sanctions and consequences” for if Assad’s regime persists with the brutal conflict.

“The future must not belong to a dictator who massacres his people,” Obama told the U.N. General Assembly.

“If there is a cause that cries out for protest in the world today, it is a regime that tortures children and shoots rockets at apartment buildings.”

He told leaders at the U.N. headquarters: “As we meet here, we again declare that the regime of Bashar al-Assad must come to an end so that the suffering of the Syrian people can stop, and a new dawn can begin.”

Obama also warned that the international community must act to prevent the 18 month old uprising against Assad turning into “a cycle of sectarian violence.”

He said the United States wants a Syria “that is united and inclusive; where children don’t need to fear their own government, and all Syrians have a say in how they are governed — Sunnis and Alawites; Kurds and Christians.”

“That is the outcome that we will work for — with sanctions and consequences for those who persecute; and assistance and support for those who work for this common good,” Obama said.

“We believe that the Syrians who embrace this vision will have the strength and legitimacy to lead.”

Syria is one of the key topics at the U.N. assembly with growing western calls for action against Assad. Russia and China have vetoed three U.N. Security Council resolutions which could have led to sanctions.