Despite blocking IAEA inspectors from tracking uranium enrichment, Tehran says diplomatic channels remain open.
The International Atomic Energy Agency said its inspectors have left Iran, just two days after the country suspended cooperation with the United Nations' nuclear watchdog agency.
The move comes as experts warn that the American and Israeli airstrikes on key nuclear facilities will likely drive Iran's nuclear program underground and make it harder for international observers to be certain if Tehran is building a bomb.
A prevous study on climatic and global effects of nuclear war raised awareness of the concept of "nuclear winter."
Britain, France and Germany threaten to reimpose sanctions if there is no progress on limiting Tehran's nuclear program.
Iran retaliated - and Israel and Iran risked all-out war - after IAEA board's found Tehran breached nonproliferation duties.
Nuclear-armed nations possess about 12,400 nuclear warheads, but nearly 90% belong to Russia and the U.S.
The court's advisory opinion stems from a sustained campaign led by Vanuatu and supported by 130 U.N. member nations.
The U.S. will remain a full member of UNESCO until its withdrawal officially takes effect at the close of next year.
Experts call it a 'slow-moving global catastrophe' for food, energy, and trade that will require systematic monitoring.
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