Obama: U.S. cannot solve the world's problems alone

President Obama told the United Nations on Monday that they must all work together on an array of challenges — from Syria to Ukraine, from poverty to climate change — because "the United States cannot solve the world's problems alone."

While making a largely thematic address to the U.N. General Assembly about the need for global cooperation, Obama also had harsh words for Russia just hours ahead of a tense meeting with President Vladimir Putin later on Monday.

The president criticized Russia's aggression in eastern Ukraine and its annexation of Crimea, saying "we cannot stand by when the sovereignty and territorial integrity of a nation is flagrantly violated."