UNITED NATIONS— President Barack Obama challenged world leaders to speak out forcefully against what he called the politics of division and violence, and confront deeper causes of anger in the Muslim world.
During an address Tuesday at the United Nations General Assembly, Obama said attacks such as the one that killed U.S. Ambassador to Libya Chris Stevens and three other Americans are an assault not only on America but ideals the United Nations was founded on.
He began and ended his speech with a description of Stevens as someone who worked to bring democracy to Libya and build bridges between cultures. The United States, he said, will be relentless in bringing the killers to justice.
World leaders, Obama said, must speak out against impulses towards violence.
"If we are serious about those ideals, we must speak honestly about the deeper causes of the crisis," said Obama. "Because we face a choice between the forces that would drive us apart and the hopes we hold in common. 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."
Obama called the anti-Muslim video that sparked violence in many countries "crude and disgusting" and an insult to Muslims and to the United States. But he defended the protection of free speech in America.
He also underscored U.S. support for what he called "forces of change" in Middle Eastern and North African countries undergoing transformation in the Arab Spring.
In Syria, he said, the government of President Bashar al-Assad must come to an end, but the world must work to ensure a peaceful transition.
"In Syria, the future must not belong to a dictator who massacres his people," said Obama. "If there is a cause that cries out for protest in the world today, peaceful protest, it is a regime that tortures children and shoots rockets at apartment buildings. And we must remain engaged to assure that what began with citizens demanding their rights does not end in a cycle of sectarian violence."
Obama said a "season of progress" has not been limited to the Arab world. He cited peaceful transitions in Africa, and in Burma, adding that recent turmoil also shows that democracy is hard work.
"True democracy demands that citizens cannot be thrown in jail because of what they believe, and businesses can be opened without paying a bribe," said Obama. "It depends on the freedom of citizens to speak their minds and assemble without fear; on the rule of law and due process that guarantees the rights of all people. In other words, true democracy - real freedom - is hard work."
Obama also spoke about the standoff with Iran over its nuclear program, which the U.S., Israel and other nations believe is aimed at developing a nuclear weapon. Iran says its program is for peaceful purposes.
While he mentioned no "red line" for Iran that could trigger military action against its facilities, he said time for a diplomatic solution is not unlimited and the U.S. will do what it must to prevent Iran from obtaining a nuclear weapon.
"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," said Obama.
Before leaving New York, President Obama delivered remarks to the Clinton Global Initiative headed by former president Bill Clinton.
Republican presidential nominee Mitt Romney also addressed the organization, calling for a new approach to U.S. foreign aid. He indirectly criticized President Obama's Middle East policies, saying Americans are "troubled" by developments there.