The United States gave Iran a March deadline to start cooperating with a U.N. nuclear agency investigation Thursday, news sources report.
U.S. diplomat Robert Wood made the announcement to the board of the International Atomic Energy Agency, a 35-nation board, The Daily Star reported.
Iran was first reported to the U.N. Security Council about its nuclear program by the IAEA in 2006 and was then given U.N. sanctions, The Daily Star reported.
Last year, the IAEA published an intelligence report that revealed past - and potentially continuing - research in Iran that could be related to nuclear weapons. Since then, the IAEA has tried to gain access to Iranian sites for inquiry, but to no avail, The Daily Star reported.
Iran denies it is on a quest for atomic bomb capability, but it has refused to curb nuclear work with both civilian and military applications. The US has become increasingly frustrated by the country's refusal to be transparent with the IAEA, Reuters reported.
"If by March Iran has not begun substantive cooperation with the IAEA, the United States will work with other board members to pursue appropriate board action, and would urge the board to consider reporting this lack of progress to the U.N. Security Council," Wood said in a statement, Reuters reported.
A simple majority in the IAEA board would be required to refer an issue to the U.N. Security Council, which has put four sanctions resolutions on Iran in the last six years, Reuters reported.