* Russia wouldn’t block consensus for more Iran sanctions
* Patience eroding after Iran vows major nuclear expansion
* UN nuclear watchdog in "stormy situation", new chief says
* IAEA demands Iran clarify new uranium enrichment plans
By Oleg Shchedrov
MOSCOW, Dec 1 (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.
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.
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 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 be 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.
IRAN‘S BEHAVIOUR SAID TO UNDERMINE DIALOGUE
Iran’s plan for 10 more enrichment plants did "not add optimism to talks", he said, in a reference to negotiations with Tehran revived in October but stalled by disputes.
The United States and its allies fear Iran will divert its declared civilian nuclear energy programme 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.
Iran said on Tuesday it would take unspecified legal action over the IAEA governors’ resolution, and provide Iranians with enough gasoline in order to trump any broader U.N. sanctions.
Iranian Foreign Minister Manouchehr Mottaki will "declare the Islamic Republic’s appreciation or opposition" by letter to IAEA board members depending on how they voted, ministry spokesman Ramin Mehmanparast told a news conference.
The official news agency IRNA quoted Mehmanparast as saying Iran would complain to countries that voted against it.
But this would not change Iran’s relations with Russia and China, which are both important trade partners.
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.
They say U.N. sanctions would make it hard for Iran to muster the needed equipment, Iran appears to lack sufficient uranium reserves, and its current enrichment work at Natanz seems to be limited by technical difficulties.
But all this, analysts say, would not rule out the risk 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. (Additional reporting by Andrew Hammond in Dubai and Sylvia Westall in Vienna; Writing by Mark Heinrich; editing by Angus MacSwan)
((email@example.com; +43 1 5311 2276; Reuters Messaging: firstname.lastname@example.org))