By Louis Charbonneau and Michelle Nichols UNITED NATIONS (Reuters) - The United States is reviewing and seeking to confirm reports that Iran launched a ballistic missile last month in violation of U.N. Security Council resolutions, U.S. Ambassador to the United Nations Samantha Power said on Tuesday. "The U.S. is conducting a serious review of the reported incident," Power told reporters after a meeting of the Security Council on unrelated issues.