In words clearly directed at Iran, Obama specified that "we will not tolerate the development or use of weapons of mass destruction."
"Just as we consider the use of chemical weapons in Syria to be a threat to our own national security, we reject the development of nuclear weapons that could trigger a nuclear arms race in the region, and undermine the global non-proliferation regime," he said.
Noting that the United States was emerging from a "perpetual war footing" after more than a decade of conflict in Iraq and Afghanistan, Obama acknowledged that unilateral American action -- particularly military action -- was unable to achieve the desired development of democratic systems, open markets and respect for human rights around the world.
"Iraq shows us that democracy cannot be imposed by force," he said.
Obama also directed a challenge to his fellow world leaders, noting that the United Nations was created in ashes of World War II so that nations could work together to confront global challenges and conflict.
"The question is whether we possess the wisdom and the courage as nation states and members of the international community to squarely meet those challenges; for the United Nations to meet the challenges of our time," he said.
That means answering the inevitable call for action, Obama said.
"While the U.N. was designed to prevent wars between states, increasingly we face the challenge of preventing slaughter within states," he said, adding that "in such moments, the international community will need to acknowledge that the multilateral use of military force may be required to prevent the very worst from occurring."