U.S. President Barack Obama says he will take direct action when it is necessary to defend the United States against terrorist attacks, and use "all elements of U.S. power, including military force, to secure U.S. interests in the Middle East."
Speaking to world leaders at the U.N. General Assembly in New York, President Obama urged "consequences" for the use of chemical weapons in Syria and elsewhere, warning the world's credibility is at stake.
Earlier, U.N. Secretary-General Ban Ki-moon opened the annual meeting by appealing to world leaders to stop sending weapons to Syria.
Mr. Ban appealed to "all states to stop fueling the bloodshed and to end the arms flows to all parties."
He called for the Security Council to adopt an "enforceable" resolution on a U.S.-Russian agreement to put Syria's chemical weapons under international control for future destruction.
Mr. Obama said the United States wants "transparent" and "concrete" actions from Iran on its nuclear development program. He said he is determined to seek a diplomatic path to end the issue.
Mr. Obama spoke hours before Iranian President Hassan Rouhani, who urged Western leaders Monday to engage Iran and ease painful economic sanctions against his country.
Those sanctions stem from concerns that Iran is seeking to develop nuclear weapons and its repeated refusal to heed U.N. demands to suspend uranium enrichment. Iran insists its nuclear program is solely for peaceful purposes.
U.S. officials say there is no meeting scheduled between Mr. Obama and Mr. Rouhani while they are in New York, but have not ruled out the possibility. U.S. and Iranian government heads have not met since before the 1979 Islamic revolution that toppled the U.S.-backed Shah.