MOSCOW (Reuters) - Russia will join any consensus on more sanctions against Iran, a senior Russian diplomatic source said on Tuesday after Tehran declared it would expand nuclear activity in defiance of a U.N. rebuke.

Iran's President Mahmoud Ahmadinejad attends a news conference in Brasilia in this November 23, 2009 file photo. REUTERS/Ricardo Moraes

It was a thinly veiled Russian warning to Iran of waning patience with its failure to allay fears it aims to develop atom bombs in secret, and hinted that Iran could no longer rely on Russia to stop tougher world action against it.

Iranian President Mahmoud Ahmadinejad voiced defiance on Tuesday, saying sanctions would have no effect and that no more talks on the nuclear dispute were needed with the West. Speaking on state television, he also criticized Russian action.

Governors of the U.N. nuclear agency passed a resolution on Friday censuring Iran for covertly constructing a second enrichment plant near the holy city of Qom, in addition to its IAEA-monitored one at Natanz, and demanding a construction halt.

Tehran said on Sunday it would build 10 more uranium enrichment sites -- a pledge that Ahmadinejad said on Tuesday was “not a bluff”.

Iran’s announcement had been in retaliation for the 25-3 vote by the International Atomic Energy Agency’s 35-nation Board of Governors, which sailed through with unusual Russian and Chinese support.

“If there is a consensus on Iran sanctions, we will not stand aside,” said the Russian diplomatic source, who requested anonymity due to the sensitivity of the situation.

By referring to “consensus”, Russia could be leaving itself an escape hatch since China has been the most resistant to punitive steps against Iran among the six world powers.

The source made clear Moscow would not move so fast to embrace harsher sanctions as the United States and EU powers, who want to act early next year if Tehran has not begun fulfilling IAEA demands for nuclear restraint and transparency by then.

“We will be thinking about sanctions but this is not an issue of the next few hours or weeks,” he said.

Russia did not want to complicate the situation with threats against Iran.

“We would rather have Iran cooperating more openly and consistently with the IAEA and showing clear steps to lift concerns -- which are gaining greater foundation -- than introducing sanctions against Iran,” the source said.

AHMADINEJAD RESPONSE

In his televised comments, Ahmadinejad dismissed the threat of sanctions and warned any “aggressor” against Iran.

“Sanctions will have no effect. Aggressors will regret their action as soon as they put their finger on the trigger,” he said.

Israel has hinted at the possibility of attacking Iranian facilities if it deems diplomacy at a dead end.

Ahmadinejad said Western attempts to isolate Iran were in vain and he criticized Russia.

“Russia made a mistake by backing the anti-Iran resolution and we believe that their analysis in this regard was incorrect,” he said.

The Russian source said Iran’s plan for 10 more enrichment plants did “not add optimism to talks”, in a reference to talks with Tehran revived in October but stalled by disputes.

The United States and its allies fear Iran will divert its declared civilian nuclear energy program to yielding atomic bombs, not electricity. Tehran says it has no such intention.

Concerns have deepened over Iran’s retreat from an October deal in principle that would see its low-enriched uranium -- which is potential fissile material for bombs -- sent abroad for processing into fuel for a nuclear medicine reactor in Tehran.

“The situation surrounding the agency is stormy now. We have a lot of difficult challenges,” new IAEA Director-General Yukiya Amano told reporters on his first day in office after succeeding Mohamed ElBaradei. Amano declined to elaborate.

IAEA spokeswoman Gill Tudor said Iran had not yet informed the U.N. nuclear inspectorate directly of its new enrichment plans and that it would seek clarification from Tehran.

Western diplomats and analysts believe the new enrichment plan may be largely bluster, possibly a negotiating gambit by Iran, and would take many years if not decades to execute.

But analysts said the risk remained of Iran using an array of above-board civilian enrichment plants to camouflage one or two small covert sites geared to enriching uranium to the high purity suitable for nuclear warheads.