By Mark Felsenthal and Amena Bakr
UNITED NATIONS (Reuters) - President Barack Obama urged world leaders on Tuesday to put an end to the intolerance and violence that led to the recent killing of the U.S. ambassador in Libya and warned Iran he would do what it takes to prevent Tehran from getting nuclear arms.
In a 30-minute address to the 193-nation U.N. General Assembly, Obama called anew for the ouster of Syrian President Bashar al-Assad following an 18-month civil war without saying how to make it happen. He also offered no fresh ideas on solving the Israeli-Palestinian conflict.
Beginning and ending his remarks by evoking Christopher Stevens, the U.S. ambassador to Libya who died with three other Americans in a September 11 assault on the American Consulate in Benghazi, Obama called on nations to fight such violence.
"Today, we must affirm that our future will be determined by people like Chris Stevens, and not by his killers," said Obama, who seeks re-election on November 6. "Today, we must declare that this violence and intolerance has no place among our United Nations."
While condemning the violence sparked by a video made in California that depicts the Prophet Mohammad as a womanizer, fool and child abuser, several Muslim leaders called for international action to outlaw acts of blasphemy.
U.S. missions also came under attack in Egypt, Tunisia, Indonesia and other Muslim nations.
Obama - while repeating his condemnations of the video as "crude and disgusting" and stressing that the U.S. government had nothing to do with its production - staunchly defended free speech.
"The strongest weapon against hateful speech is not repression, it is more speech - the voices of tolerance that rally against bigotry and blasphemy," Obama said.
Saying it is necessary to "honestly address the tensions between the West and the Arab world" moving toward democracy, Obama said he did not expect everyone to agree with him.
"However, I do believe that it is the obligation of all leaders in all countries to speak out forcefully against violence and extremism," he said. "There is no speech that justifies mindless violence."
'CALL ME AWFUL THINGS'
"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 said, drawing applause and some laughter.
The U.S. view, however, was not embraced by all sides at the General Assembly.
Afghan President Hamid Karzai took aim both at the anti-Islam video and publication of cartoons depicting the Prophet Mohammad - the latter occurring most recently in France.
Karzai called the insults to the faith of 1.5 billion Muslims, the "depravity of fanatics," and added: "Such acts can never be justified as freedom of speech or expression."
Pakistani President Asif Ali Zardari said violence could not be condoned, but he added that "the international community must not become (a) silent observer and should criminalize such acts that destroy the peace of the world and endanger the world security by misusing freedom of expression."
Egypt's new president, Mohamed Mursi, said freedom of expression carried with it responsibilities, and Susilo Bambang Yudhoyono, president of the world's most-populous Muslim-majority nation, Indonesia, called for a binding international treaty to "prevent incitement to hostility or violence based on religions or beliefs."
Earlier on Tuesday in Geneva, the Organization of Islamic Cooperation - the world's largest Islamic body, representing 56 countries - called for expressions of "Islamophobia" to be curbed by law in the same way as some countries restrict anti-Semitic speech or Holocaust denial.
Obama offered no fresh ideas on how to solve two crises - the civil war in Syria and the suspicion that Iran is seeking nuclear weapons - that the U.N. Security Council has been unable to resolve.
On Monday, Iranian President Mahmoud Ahmadinejad spoke of Israel being "eliminated" and said he did not take seriously its threats to strike Iran's nuclear facilities. He said his nation is committed to seeking a negotiated solution.
Iran says its nuclear program is solely for peaceful uses such as generating electricity or producing medical isotopes.
"Let me be clear: America wants to resolve this issue through diplomacy and we believe that there is still time and space to do so. But that time is not unlimited," Obama said.
"The United States will do what we must to prevent Iran from obtaining a nuclear weapon," he added, without providing specifics.
'THE BLOODSHED IN SYRIA'
While some nations, notably in the Arab world, have called for more international action to stop the violence in Syria, the U.N. Security Council has been deadlocked, and Russia and China have vetoed three resolutions condemning Assad's government. Qatar said it was time for action outside the United Nations.
"I think that it is better for the Arab countries themselves to interfere out of their national, humanitarian, political and military duties and do what is necessary to stop the bloodshed in Syria," Qatari Emir Sheikh Hamad bin Khalifa al-Thani said.
Syria has accused Qatar, Saudi Arabia and Turkey of supplying arms to the Syrian rebels.
The United Nations must immediately provide protection to areas liberated by rebels in Syria, French President Francois Hollande told the General Assembly.
U.S. officials have privately made clear that they have no appetite for a military intervention without U.N. sanction in another Muslim country just as they have wound down the U.S. war in Iraq and are largely pulling out of Afghanistan by 2014.
"The international community should not look the other way as violence spirals out of control," U.N. Secretary-General Ban Ki-moon said.
Brazilian President Dilma Rousseff sounded a note of caution. "There is no military solution to the Syrian crisis," she told the General Assembly. "Diplomacy and dialogue are not just our best option, they are the only option."
A year after the Palestinians mounted an ultimately failed effort for U.N. membership, Obama passed quickly over the Arab-Israeli conflict.
"The road is hard, but the destination is clear - a secure Jewish state of Israel and an independent, prosperous Palestine," Obama said. "America will walk alongside all who are prepared to make that journey."
Ban offered a pessimistic assessment, suggesting that time has nearly run out for such a negotiated solution. "The two-state solution is the only sustainable option. Yet the door may be closing, for good," he said.
(Writing by Arshad Mohammed; Additional reporting by Matt Spetalnick, Brian Winter, David Brunnstrom, Louis Charbonneau and Michelle Nichols; Editing by Will Dunham and Eric Beech)