The United Nations nuclear watchdog's governing body voted overwhelmingly on Friday to censure Iran for developing a uranium enrichment site in secret, and demanded it freeze the project immediately.
The resolution, passed by a 25-3 margin with six absentions, was the first by the 35-nation governing board in almost four years. With rare Russian and Chinese backing, it sent a message of international exasperation with Iran's nuclear secrecy and defiance.
But it was unclear whether the measure, sponsored by six world powers, would translate into crucial Russian-Chinese support for painful sanctions that Western leaders may push for if Iran does not begin to dispel fears about its nuclear ambitions soon.
Most developing nations on the International Atomic Energy Agency board, who are in a bloc that includes Iran, opposed the move, saying it would be provocative and counterproductive. Iran warned it would undermine its relations with the IAEA.
But supporters were provoked by the September revelation of a second enrichment site Iran had been building for at least two years, a subterfuge they said fanned suspicions of more secret sites that could be dedicated to making atom bombs.
Iran: Resolution jeopardizes nuclear talks
An Iranian official said that the resolution jeopardizes talks between Tehran and six world powers on its atomic program and harms its cooperation with the agency.
"Adoption of this resolution is not only unhelpful in improving the current situation, but it will jeopardise the conducive environment vitally needed for success in the process of Geneva and Vienna negotiations expected to lead to a common understanding," Ambassador Ali Asghar Soltanieh said.
In a statement, he said the resolution was a "hasty and undue" step imposed by a small number of IAEA board members. "This resolution will of course damage the existing environment of cooperation with the IAEA," Soltanieh later told reporters on the sidelines of the meeting.
He said Iran would end its "voluntary gestures" of cooperation to the IAEA, but did not specify details.
The measure also signaled diminishing tolerance of Iran's reluctance to embrace an IAEA-brokered plan to provide it with fuel for a nuclear medicine reactor if it gives up enriched uranium that could be turned into bomb material if further refined.
The draft resolution urged Iran to immediately halt construction of the Fordow enrichment plant, located in a mountain bunker, and to clarify its original purpose and confirm it has no more hidden atomic facilities or clandestine plans for any. Iran denies it wants to build nuclear weapons, saying its atomic energy program is purely for peaceful purposes.