LONDON (Reuters) - A military raid on Iran's nuclear facilities would wreak such profound damage on global prosperity and security that other means -- principally a mix of sanctions and sabotage -- must remain the levers of pressure on Tehran.
So says conventional wisdom among opinion-makers in Europe, who fear Iran could retaliate to an attack by lashing out in the Gulf and temporarily severing the marine and pipeline arteries supplying a large part of global oil and gas demand.
"You are talking about creating a wounded bear with very unpredictable consequences," Malcolm Chalmers, research director at Britain's Royal United Services Institute, told Reuters.
Bruce Riedel, a former senior CIA analyst who has advised the Obama White House on policy in the region, told Reuters: "Sabotage and sanctions have set Iran back considerably. A military strike now would undermine the international consensus on Iran, achieve little and risk heavy retaliation."
And after grinding conflicts in Afghanistan and Iraq and a campaign in Libya just completed, the West is too war-weary and preoccupied with repairing cash-strapped economies to contemplate another conflict, a parallel line of argument goes.
Valid though these arguments are widely seen to be in the West, the political and diplomatic calendar suggests such views will come under unprecedented scrutiny in coming months.
The pre-eminence of sanctions and covert action in the West's policy mix on Iran will come under the spotlight next week when the U.N. nuclear watchdog publishes a report on Iran's nuclear programme.
The report by the International Atomic Energy Agency (IAEA) is expected to unveil detailed intelligence pointing to military dimensions of Iran's nuclear programme, while stopping short of saying explicitly that Tehran is trying to build such weapons.
Iran says its nuclear programme is peaceful.
Some of Iran's foes are expected to react to the report by calling for armed action to rise higher up the list of options for stopping Iranian nuclear activities that the West suspects are aimed at developing an atomic weapon capability.
Those calls may get a more sympathetic hearing than usual in the United States, which said last month it had foiled an alleged Iranian attempt to assassinate the Saudi Arabia ambassador in Washington. Iran, estranged from the United States since its 1979 revolution, denies any such plot.
"There has been a very clear pattern of sabre-rattling to coincide with efforts to tighten sanctions," Trita Parsi, an expert on U.S.-Iranian relations, told Reuters.
"Israelis use the tactic of talking tough about a military option in order to pressure Washington to take further action on Iran. In turn, the U.S. and UK use the same tactic to pressure other countries to tighten sanctions."
"The question is, to what extent can this tactic be used without becoming a self-fulfilling prophecy? At some point, the ability to carry out a strike may be called into question."
Following next week's report, Israel is likely to repeat its message that arch-foe Iran is a global menace and a window of opportunity for a solution is closing.
Israel test-fired a missile on Wednesday amid heightened public debate in the Jewish state over the possibility of a pre-emptive attack on Iran's nuclear sites.
U.S. President Barack Obama says he hopes the alleged assassination plot will lead to tighter sanctions against Iran, already under U.N. sanctions over its nuclear programme.
And Obama, like some other Western leaders, is likely to react to the report by reiterating loudly that all options -- meaning a military strike -- remain on the table.
On Wednesday, a British official said his country was keeping its options open in relation to military action against Iran, after a newspaper reported it was stepping up contingency plans amid rising concerns over Tehran's nuclear ambitions.
But some analysts argue that, for now, Western powers are talking tough merely as a tactic to create leverage to achieve their principal goal, namely tightening sanctions. In reality, they are deeply cautious about any military action.
That's partly due to the enormous risks such a raid would entail and partly because it would be very difficult to do.
"It has been, and remains, a possibility that there could be military action," said RUSI's Chalmers.
"But the calculus on the risk side I don't think has changed substantially, because it's completely unknown what the consequences of such action would be.
"What would start off as something motivated by the nuclear programme would have a high probability of turning into a much broader conflict," Chalmers said.
Analysts say the likely consequences would include:
-- Iran expelling IAEA inspectors and withdrawing from the Nuclear Non-Proliferation Treaty, in effect ending any possibility of a negotiated solution to the nuclear issue
-- The end of any international consensus on the Iranian nuclear question
-- The snuffing out of residual support for Iran's reformist "Green movement" as Iranians rallied around the government
-- Iran temporarily closing the Gulf to oil exports, leading to an economically damaging spike in oil prices
-- Iran inflaming anti-U.S. sentiment in Muslim countries, especially Syria, Lebanon and the Palestinian Territories
-- Loss of any Arab goodwill towards the West generated by Western support for Arab uprisings.
Chalmers said that within the option of military strikes "there's the problem of 'how much is enough'?" There would be a temptation to destroy Iranian air defences "and you end up with a strike against a large part of the military infrastructure".
Peter Crail, non-proliferation analyst at the Washington-based Arms Control Association, an advocacy and research group, wrote in a note that military strikes by the United States and Israel "would only achieve a temporary delay in Iran's nuclear activities and would result in costly consequences for U.S. and regional security and the U.S. and global economy".
Pieter Wezeman, a researcher on military issues at the Stockholm International Peace Research Institute, said Iran's nuclear work was spread out over Iran and if it was a clandestine weapons capability "then we have to assume that Iran would make all efforts to protect it...(most importantly) by hiding and dispersing those sites".
"So it would be very, very difficult for Israel to mount an attack and to be sure they destroy all essential facilities and Israel clearly has not the means to start a full-out air campaign against Iran."
Douglas Barrie, aerospace analyst at the International Institute for Strategic Studies, said Western arms companies were developing some "very, very large air dropped weapons designed to penetrated very heavily protected targets".
But "in general one of the hardest targets to go against is a buried target, not the least because you've got to find it in the first place", he said.
Contacted for comment, a Western official who declined to be identified due to the sensitivity of the subject, said without elaborating that Iran had evidently sought to bury nuclear-related facilities at considerable depths.
Tarak Barkawi, a senior lecturer in war studies at Cambridge University, told Reuters: "I find it incredible that they would consider something so stupid, but I don't entirely dismiss the possibility that something like this would happen."
He said this was because of the position of Israel, Washington's close ally and Iran's arch foe. What pressure Israel was putting on Washington over Iran privately was "the back story to this issue", he said.
Parsi said that the electoral calendar in the United States may have a bearing on the way the debate developed.
While a strike was generally considered unlikely, he said, Israel might feel that now was an opportune for a raid because Obama, facing re-election and seeking votes from supporters of Israel, had limited scope to retaliate against Israel.
"He may feel he cannot afford another confrontation with (Israeli Prime Minister Benjamin) Netanyahu," Parsi said.
Additional reporting by Adrian Croft, Tim Castle, Mark Hosenball and Matt Scuffham in London, Fredrik Dahl in Vienna and David Brunnstrom in Brussels; Editing by Alistair Lyon