The United States on Thursday, November 29 set a March deadline for Iran to start cooperating in substance with a U.N. nuclear agency investigation, warning Tehran the issue may otherwise be referred to the U.N. Security Council, Reuters reported. The comments by U.S. diplomat Robert Wood to the board of the International Atomic Energy Agency signaled Washington’s growing frustration at a lack of progress in the IAEA’s inquiry into possible military dimensions to Tehran’s nuclear program. In his statement, Wood requested IAEA Director-General Yukiya Amano to say in his next quarterly report on Iran, likely due in late February, whether Tehran has taken “any substantive steps” to address the agency’s concerns. Iran was first reported to the U.N. Security Council over its nuclear program by the IAEA’s 35-nation board in 2006 and then was hit by U.N. sanctions.