United Nations  — The United States will “do what we must” to prevent Iran from developing a nuclear weapon, President Barack Obama is expected to tell the United Nations General Assembly Tuesday in a speech that will also touch heavily on the death of U.S. Ambassador Christopher Stevens in Libya.

“We respect the right of nations to access peaceful nuclear power, but one of the purposes of the United Nations is to see that we harness that power for peace,” Obama will tell U.N. delegates, according to excerpts of his planned remarks made available by the White House. “Make no mistake: a nuclear-armed Iran is not a challenge that can be contained.”

Obama’s scheduled speech comes on the opening day of the U.N. General Assembly debate session.

During the session, which ends October 1, world leaders will again take up a host of pressing humanitarian issues, including poverty, global warming and the prospect of renewed conflicts in sub-Saharan Africa. But the Middle East and the 18-month civil war in Syria are expected to remain center stage.

In his speech Tuesday morning, Obama is expected to say that while the United States remains committed to a diplomatic solution on Iran’s nuclear program, “time is not unlimited.”

While Iranian leaders say their nuclear program is for peaceful purposes, Western leaders believe Tehran wants to build a nuclear weapon. U.N. inspectors also have expressed doubts about the program’s aims.

The consequences of a nuclear-armed Iran are immense, Obama will tell delegates.

“It would threaten the elimination of Israel, the security of Gulf nations, and the stability of the global economy. It risks triggering a nuclear-arms race in the region, and the unraveling of the non-proliferation treaty,” the president will say.

Obama’s speech comes on the heels of a series of confrontational statements by Iranian President Mahmoud Ahmadinejad, who declared Monday that Israel has “no roots in the Middle East.”

U.S. national security spokesman Thomas Vietor called the comments “disgusting, offensive and outrageous,” and said they “underscore again why America’s commitment to the security of Israel must be unshakeable, and why the world must hold Iran accountable for its utter failure to meet its obligations.”

Later, in an interview on CNN’s “Piers Morgan Tonight” Monday, Ahmadinejad appeared to say he would not be surprised if Israel attacks Iran over its nuclear program.

“Of course, the Zionists are very much — very adventuresome, very much seeking to fabricate things,” Ahmadinejad said, referring to Israel. “And I think they see themselves at the end of the line. And I do firmly believe that they seek to create the opportunities for themselves and their adventurous behaviors.”

In his speech, Obama will also address the recent wave of violence targeting the United States, including the September 11 attack in Benghazi, Libya, that left Stevens, the U.S. ambassador, dead.

“The attacks of the last two weeks are not simply an assault on America. They are also an assault on the very ideals upon which the United Nations was founded,” Obama is expected to say.

“If we are serious about those ideals, we must speak honestly about the deeper causes of this crisis. Because we face a choice between the forces that would drive us apart, and the hopes we hold in common,” the president will say.

Obama also will address the uproar across the Muslim world over “The Innocence of Muslims,” a movie produced in the United States that mocked the Muslim Prophet Mohammed.

“There are no words that excuse the killing of innocents,” Obama will say, according to 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.”

While Obama is speaking in front of an international crowd, his speech Tuesday will also largely target a domestic audience, which will decide in November whether he gets another chance at the presidency.

Later Tuesday, French President Francois Hollande is scheduled to take the lectern and is expected to address a worsening crisis in the Sahel, where a deadly mix of drought, famine and Islamic militancy have plagued the North Africa region.

more at:  http://www.cnn.com/2012/09/25/world/new-york-unga/index.html