Iran nuclear: Russia's Lavrov warns against attack
The Russian foreign minister has warned that a Western military strike against Iran would be "a catastrophe".
Sergei Lavrov said an attack would lead to "large flows" of refugees from Iran and would "fan the flames" of sectarian tension in the Middle East.
Israeli Defence Minister Ehud Barak earlier said any decision on an Israeli attack on Iran was "very far off".
Meanwhile, Iran's foreign minister said talks on its nuclear programme would "most probably" take place in Istanbul.
Ali Akbar Salehi told reporters during a visit to Turkey that negotiations were going on about venue and date, and the timings would be settled soon.
But the UK Foreign Office said that there were "no dates or concrete plans" for talks, as Tehran was "yet to demonstrate clearly that it is willing to respond to [EU foreign policy chief] Baroness Ashton's letter and negotiate without preconditions.
"Until it does so, the international community will only increase pressure on it through further peaceful and legitimate sanctions."
Talks between Iran and six world powers - the US, UK, China, France, Russia and Germany - were last held in Istanbul a year ago but no progress was made.
A Western diplomat told the BBC that Iran was "chasing headlines" and "pretending that it was ready to engage". Tehran was "more interested in propaganda" than in sitting down without preconditions, he said.
Tensions with Iran have risen in recent weeks after the UN's nuclear monitors confirmed Tehran was producing 20% enriched uranium at its Fordo plant near Qom.
The US and its allies suspect the Islamic Republic of secretly trying to develop a nuclear weapons capacity but Iran insists its programme is peaceful.
The US has recently imposed sanctions on Iran's central bank and against three oil companies which trade with the country. The European Union has said it will place an embargo on Iran's oil exports.
For its part, Iran has threatened to block the transport of oil through the Strait of Hormuz, a key shipping route.
The comments from Russia's foreign minister included criticism of the Western moves to strengthen sanctions on the Islamic Republic, which he said were aimed at "stifling" Iran's economy.
Mr Lavrov told journalists in Moscow that they would have to ask those who he said were "talking constantly" about a military attack to find out if it would occur. He said such an attack would start off a "chain reaction" and he did not know how that would end.
Israel - thought to be the only nuclear power in the region - has said it could launch a military strike against Iran to prevent it developing nuclear weapons.
Last week, Iran blamed Israel and the US for the death of Mostafa Ahmadi-Roshan, an Iranian nuclear scientist apparently killed by a bomb targeting his car in Tehran.
BBC diplomatic correspondent Jonathan Marcus says Mr Barak's comments can be seen as an attempt to placate the Americans, who are growing concerned that Israel may take military action against Iran without alerting Washington in advance.
The Israeli defence minister, speaking on Israel's army radio, implied that any plans would be co-ordinated with the US.
"I don't think our ties with the United States are such that they have no idea what we are talking about," he said.
The US defence chief General Martin Dempsey is due to arrive in Israel on Thursday for his first visit since becoming chairman of the joint chiefs of staff in September. On his agenda are meetings with various Israeli officials including Mr Barak.
Haaretz reports that Israel will present Gen Dempsey with an intelligence assessment that indicates Iran has "not yet decided" whether to make a nuclear bomb.
It is not clear when Iran might make the decision to use its nuclear capabilities to manufacture a weapon, the paper says.