The head of the United Nations nuclear watchdog has said Iran is refusing to provide details of its nuclear activities.
Yukio Amano, director-general of the International Atomic Energy Agency (IAEA), issued his warning at the UN General Assembly on November 5.
He said talks with Iran have intensified this year after an IAEA report in November 2011 said it had "credible information that Iran had carried out activities relevant to the development of a nuclear explosive device."
But Amano said efforts to persuade Iran to give more information on its nuclear program had produced "no concrete results."
Tehran has said its nuclear development program is for civilian purposes.
Western governments, who have placed financial sanctions on Tehran, accuse it of pursuing a nuclear-weapons program.
Fresh reports from Israel
suggest that Prime Minister Benjamin Netanyahu and Defense Minister Ehud Barak were rebuffed by Israel's military in 2010 when they ordered it to prepare for a possible attack on Iran's nuclear facilities.
Observers are said to be following closely the amount of 20-percent-enriched uranium that Iran is accumulating, since such material lends itself to the 90-percent level required for a nuclear bomb.
Barak claimed last week
in an interview with Britain's "The Daily Telegraph" that Iran had used one-third of its enriched uranium to make fuel rods for a medical research reactor -- possibly delaying progress toward a nuclear "red line" that Israel insists Iran must not cross.
But he insisted that Israel still believed Iranian authorities were seeking nuclear weapons and must be prevented from developing them.
The United States has warned that it is "unacceptable" for Iran to become a nuclear-armed state.
The UN Security Council has passed four rounds of sanctions in an effort to dissuade Iran from sensitive nuclear and missile work.
Based on reporting by AFP, Reuters, and AP