Iranian officials had vowed that such work would be restarted by today after inspectors from the UN’s nuclear watchdog agency supervised the removal of seals at research facilities.
In Washington, the United States said each of the five permanent members of the UN Security Council -- all of them nuclear powers -- has told Iran to abandon plans for new atomic research activities.
U.S. State Department spokesman Sean McCormack said Washington has been working closely with the other four permanent Security Council members -- Russia, China, France, and Britain -- to send a clear message to the Iranians.
McCormack said Iran could end up facing possible sanctions in the Security Council for defying the international community. Iran says its nuclear program is peaceful and denies U.S. allegations that it is secretly trying to develop atomic weapons.