VIENNA - U.N. nuclear watchdog governors voted on Friday to rebuke Iran for building a uranium enrichment plant in secret but Tehran dismissed the move as intimidation which would poison its negotiations with world powers.

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 has clandestine plans to build nuclear bombs.

It passed by a 25-3 margin with six abstentions, smoothed by rare backing from Russia and China, which have blocked global attempts to isolate Iran, a trade partner for both, in the past.

Russia called on Iran to react with full seriousness to the signal contained in the resolution ... and to ensure full cooperation with the agency. Moscow and Beijing's support is seen as vital to the success of international pressure on Iran.

The vote reflected exasperation with Iran's retreat from an IAEA-brokered draft deal to provide it with fuel for a medical nuclear reactor if it agreed to part with its enriched uranium, which could be turned into bomb material if further refined.

British Prime Minister Gordon Brown said major powers would have to pursue harsher sanctions against Iran if it ignored the vote. This, he said during a visit to Trinidad, sent the clearest possible signal to Iran that they should desist from their nuclear plans, that the world knows what they are doing.

U.S. IAEA envoy Glyn Davies called the resolution a signal that patience is running out.

We can't have round after round of fruitless negotiations, circular negotiations that don't get us where we want to get, he said, referring to perceptions Iran is stringing out inconclusive talks to buy time to stockpile enriched uranium.

Davies said it was imperative for Iran to live up to its international obligations and offer transparency in its nuclear program, rather than carry out more evasions and unilateral re-interpretations of its obligations.

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 program is purely for peaceful purposes. But its record of clandestine nuclear work and curbs on IAEA inspections have stoked suspicions and a seven-year standoff with world powers.

Iranian Ambassador Ali Asghar Soltanieh called the resolution, which also urged Iran to immediately freeze the Fordow enrichment project hidden inside a mountain bunker, a hasty and undue step devoid of legal basis.

IRAN SAYS WILL IGNORE RESOLUTION

The great nation of Iran will never bow to pressure and intimidation vis a vis its inalienable right to peaceful uses of nuclear energy, he said.

We will not implement any word of it because this is a politically motivated gesture against the Iranian nation.

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 program an existential threat.

The last IAEA board resolution slapped on Iran was in February 2006, when governors referred Tehran's dossier to the U.N. 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.

Friday's resolution voiced serious concern at the Fordow cover-up and said this blatantly defied U.N. Security Council demands dating to 2006 for a suspension of sensitive nuclear activity to foster trust and negotiations.

Russian and Chinese support was significant since the two, who have veto power in the Security Council, have often blocked a tough united front against Iran in global policy bodies and avoided direct criticism of Tehran.

The IAEA governors also approved a plan for a uranium fuel bank, seen as a way to stem the spread of nuclear arms.

It would allow uranium producer Russia to set up an IAEA-supervised bank to provide low-enriched uranium to countries for civilian nuclear programs if they can show a perfect non-proliferation record.

(Additional reporting by Sylvia Westall; editing by Andrew Roche)

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