The resolution was the first by the 35-nation board of the International Atomic Energy Agency (IAEA) against Iran in almost four years, and a sign of growing alarm over Tehran’s failure to dispel fears it plans to build a nuclear bomb. It was passed with rare Russian and Chinese backing, by a 25-3 margin with six abstentions.

“This is a signal that patience is running out. We can’t continue talks for talks’ sake,” said US envoy to the IAEA Glyn Davies. “We can’t have round after round of fruitless negotiations, circular negotiations that don’t get us where we want to get.”

He said it was imperative for Iran to “live up to its international obligations and offer transparency in its nuclear programme, rather than carry out more evasions and unilteral re-interpretations of its obligations”.

It was unclear whether the measure, sponsored by six major powers, would translate into crucial Russian-Chinese support for painful sanctions that Western leaders will push for early next year.

The measure won blanket Western backing. Cuba, Malaysia and Venezuela, prominent in a developing nation bloc that includes Iran, voted “no”, while Afghanistan, Brazil, Egypt, Pakistan, South Africa and Turkey abstained. Azerbaijan missed the ballot.

Iran denies seeking nuclear weapons, saying its atomic energy programme is purely for peaceful purposes.

Its envoy to the IAEA, Ali Asghar Soltanieh, called the resolution a “hasty and undue” step. “This resolution will of course damage the existing environment of cooperation with the IAEA,” he later said. He added that Iran would end its “voluntary gestures” of cooperation to the IAEA.

Supporters of the resolution were provoked by the September revelation of a second enrichment site that Iran had been building for at least two years. It fanned suspicions there are more secret sites intended for making atom bombs.

The resolution urged Iran to immediately halt construction of the Fordow enrichment plant, located in a mountain bunker, and to clarify its purpose and confirm it has no more hidden atomic facilities or clandestine plans for any.

Iran has told the IAEA it developed the Fordow site in secret as a backup for other, known facilities in case they were bombed by Israel, which deems the Islamic Republic’s expanding nuclear programme “an existential threat”.

The last IAEA board resolution slapped on Iran was in February 2006, when governors referred Tehran’s dossier to the UN. Security Council over its refusal to suspend enrichment and open up completely to IAEA inspections and investigations.

Iran had assured the IAEA last year it was not hiding any nuclear-related activities in violation of transparency rules.