Western powers on Friday urged Iran to take "essential and urgent" action on issues raised by the UN's nuclear watchdog, a day after Tehran was criticized for a lack of cooperation.
On Thursday the Vienna-based International Atomic Energy Agency's board of governors passed a resolution targeting Tehran, amid an impasse over undeclared uranium particles.
"The board has sent a clear message that it is essential and urgent that Iran fulfils its (non-proliferation treaty)-required safeguards obligations," said France, Germany, Britain and the United States in a joint statement.
The nations urged Iran to "take the actions specified without delay".
The non-proliferation treaty is an international agreement aimed at preventing the spread of atomic weapons.
The same countries had brought the resolution at the IAEA, which was the second of its kind within six months regarding a lack of "technically credible" answers provided by Iran.
The watchdog has been pressing Iran to explain the presence of undeclared man-made uranium found at three sites, calling for "access to locations and material" as well as the collection of samples.
In Friday's statement, the Western powers welcomed the latest resolution and urged Iran to explain the presence of the particles.
"We hope Iran takes this opportunity to cooperate with the IAEA in good faith toward closing these outstanding matters," AFP quoted it as saying.
The resolution adopted by the IAEA's 35-nation board was carried by 26 votes in favor versus two against, with five abstentions and two countries absent, diplomats told AFP.
Russia and China voted against it.
Tehran criticized the resolution, warning it could affect cooperation with the IAEA.
The impasse over the agency's probe comes as wider talks to revive the key 2015 nuclear deal are stalled.
The agreement Iran reached with Britain, China, France, Germany, Russia and the United States gave Tehran relief from sanctions in return for guarantees it could not develop an atomic weapon.
The deal collapsed after Washington's unilateral withdrawal in 2018 under then president Donald Trump.
