"Peace will not come through statements and resolutions at the United Nations. If it were that easy, it would have been accomplished by now," added Obama.
Obama said Iran's government continues to refuse to recognize the rights of its own people, and has not demonstrated to the world that its nuclear program is peaceful.
On Syria, he said the time has come for U.N. Security Council action to sanction the Assad government and "speak with one voice" about the torture, detention and murder of people there.
"The Syrian people have shown dignity and courage in their pursuit of justice - protesting peacefully, standing silently in the streets, dying for the same values that this institution is supposed to stand for," Obama said. "The question for us is clear: Will we stand with the Syrian people, or with their oppressors?"
Obama said North Korea has yet to take concrete steps to abandon its weapons, adding that it and Iran must face greater pressure and isolation if they continue down a path outside of international law.
The president said the global financial crisis showed how interconnected nations have become and that they will "rise or fall together." The United States, he said, stands with European nations dealing with their fiscal challenges, and will work with emerging economies to promote growth.
