NEW YORK — President Obama pledged continued U.S. involvement in the turbulent Middle East at the United Nations Tuesday and vowed that the U.S. will do "what we must" to prevent Iran from obtaining a nuclear weapon.

Obama opened his remarks to the United Nations General Assembly by recalling the life of U.S. Ambassador to Libya J. Christopher Stevens, who was slain in an attack on the U.S. consulate in Benghazi, Libya.

He said the recent attacks in the Middle East were not only against America.

“They are also an assault on the very ideals upon which the United Nations was founded - the notion that people can resolve their differences peacefully; that diplomacy can take the place of war; and that in an interdependent world, all of us have a stake in working towards greater opportunity and security for our citizens.”

Under pressure from Israeli Prime Minister Benjamin Netanyahu to take a tougher stand against Iran, Obama delivered no “red line” that Iran must not cross.

He insisted the U.S. wants to resolve the issue "through diplomacy" and believes "there is still time and space to do so.”

But he said the window for diplomacy is “not unlimited," warning that 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. It risks triggering a nuclear-arms race in the region, and the unraveling of the non-proliferation treaty.”

Before Obama spoke, UN Secretary Ban ki Moon warned that the civil war in Syria was a “serious and growing threat” to the world, and called on the international community and governments in the region to bring an end to the violence.

Obama said 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.”

And he called for patience in the Middle East, saying the “turmoil of recent weeks reminds us that the path to democracy does not end with the casting of a ballot.”

He added, “true democracy demands that citizens cannot be thrown in jail because of what they believe, and businesses can be opened without paying a bribe. 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.

He again decried what he called a “crude and disgusting” anti-Islamic video that the administration at first blamed solely for the attack on the consulate in Libya as well as anti-U.S. demonstrations across the region. He said the video’s “message must be rejected by all who respect our common humanity. It is an insult not only to Muslims, but to America as well – for as the city outside these walls makes clear, we are a country that has welcomed people of every race and religion.”

He distanced the U.S. government from the creation of the video and sought to answer critics in the Middle East who have pressed the U.S. to ban such videos. He explained U.S. law and the U.S. constitution protects the right to free speech.

There was little reaction from the hushed hall during his remarks, but Obama prompted laughter when he noted that “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.”