JERUSALEM (Reuters) - If Washington is perplexed by Israeli "opacity" on whether it might attack Iran, that is no accident, since Israel's leaders are themselves torn - but also content to let fears of bluff and double-bluff play to their advantage.
Aware of daunting military difficulties and potential for diplomatic and domestic backlash should they try to hit Iran's nuclear programme, Israelis have been giving out mixed verbal signals that they hope may both encourage their U.S. ally to up the pressure on Tehran, and unnerve their Iranian enemies.
While a senior U.S. security official has told Reuters that Washington has a "sense of opacity" on what might prompt Israel to strike, few experts doubt Israel's well-funded forces could dent an Iranian atomic development programme in which it sees the makings of a mortal threat to its existence.
However, many in Israel and abroad question whether its leaders would take the risk of plunging an already volatile region into war without the full support of its U.S. ally.
Yet Prime Minister Benjamin Netanyahu may think it is a risk worth taking. Ever a big-picture thinker, the U.S.-educated premier gave a speech this week commending Israel's founding premier David Ben-Gurion for making fateful decisions at a "heavy price", despite protests heard at home and abroad.
Commentators, on the alert these days for any clue about a possible strike on Iran, spotted a subtext - that Netanyahu, too, was ready to take lonely action in Israel's interest.
He could hope for a repeat of the 1981 attack on Iraq's atomic reactor and a similar sortie against Syria in 2007, when the anger of Washington's initial reactions quickly faded.
"In the two previous experiences, even an American public, that may not have been persuaded, subsequently found out that the Israelis probably did what was necessary to be done," said Daniel Kurtzer, a former U.S. ambassador to Israel.
"So there's a huge public relations issue here: Can you make a credible case over the head of the administration, and get the American public to buy into the pain that is going to follow -- Americans being killed in terrorism, oil shock, whatever it is."
For now, Kurtzer estimated, Obama administration warnings against unilateral Israeli strikes on Iran would account for "5 percent" of Israeli deliberations, with the Netanyahu government's military calculations taking the lion's share.
Its priorities include fending off Iran's promised missile reprisals and containing potential knock-on border wars with the Lebanese and Palestinian guerrillas who are allied to Tehran.
Former Mossad spymaster Meir Dagan has predicted that Syria, Iran's key Arab ally and now beset by a bloody domestic uprising, might also choose to join in the foreign conflict.
Israeli Defence Minister Ehud Barak said last week that an Israeli attack on Iran was not imminent. He has also said there were several months left in which to decide on such action, and described Israel and the United States as coordinating closely.
But senior figures in Washington say things are less clear, with rhetoric playing an important role in the confrontation at this stage: "I don't think the administration knows what Israel is going to do. I'm not sure Israel knows what Israel is going to do," Senator Carl Levin, the chairman of the Senate Armed Services Committee told Reuters. "That's why they want to keep the other guys guessing. Keep the bad guys guessing."
Ordinary Israelis, their isolation deepening as the Arab Spring undermines U.S.-allied regimes in the region, are divided on whether to open a front with Iran. Memories of rocket salvoes from the Lebanon and Gaza wars of 2006 and 2008 still hurt.
Public reluctance has been galvanised by the unusually vocal questioning by Dagan and some other retired security chiefs of Netanyahu and Barak's secret strategising.
These critics have urged U.S.-led sanctions on Tehran be given more time. Israel and its Western partners are also widely believed to have been sabotaging Iran's uranium enrichment and ballistic arms projects, though Barak said any such covert campaign cannot be relied upon to finish the job.
A December 1 poll by the Saban Center for Middle East Policy at the U.S. think-tank Brookings found that 43 percent of Israeli Jews backed attacking Iran, while 41 percent would be opposed.
By a ratio of two to one, respondents said they would agree to stripping Israel of its own atomic arsenal as part of a regional disarmament deal. Ninety percent predicted Iran, which says its nuclear project is peaceful, would obtain in time become a nuclear military power.
Slowing its progress toward that point, however, may be enough of an objective for Israel, which Barak assessed last month stood to lose "maybe not even 500 dead" to Iranian retaliation.
Should it end up worse, "there are international mechanisms that would curtail the war between Iran and Israel", former Israeli military intelligence chief Amos Yadlin said last month.
But Yadlin, who was among the eight F-16 pilots who carried out the 1981 raid on Iraq's Osirak reactor, sounded circumspect about Israeli military capabilities against Iranian targets that are numerous, distant, fortified and on the alert for attacks - in contrast to Saddam Hussein's sole installation near Baghdad.
Israel, he said, should "open lines of dialogue with those who have superior operational abilities than we do" -- effectively, shelving unilateralism in favour of cooperation with the United States and its NATO allies.
Dan Schueftan, head of the National Security Studies Centre at Haifa University, said Israel's recent hawkish talk could be meant for foreign ears: "Because they (Netanyahu and Barak) fear that if it is believed that there is no possibility of Israel attacking Iran, the United States won't consider taking action."
Even Dagan publicly dangled the possibility that he has been playing into a propaganda ruse, telling Israeli television: "If Dagan is arguing against a conflict, then the Iranian conclusion is ... 'Listen, these Jews are crazy. They could attack Iran!'"
But posture can also be self-realising. Before launching his surprise attack on Israel at Yom Kippur in 1973, Egypt's Anwar Sadat repeatedly issued mobilisation orders to his forces while also saying he was willing to consider peace negotiations, lulling Israelis into believing Cairo was not a serious threat.
"Sadat came to be seen as desperate. But he was not bluffing," said Abraham Rabinovich, author of "The Yom Kippur War: The Epic Encounter that Transformed the Middle East".
"He clearly intended his militant statements as a signal to Israel, and the United States, that he would go to war if there was no diplomatic solution. And so it was."
Writing by Dan Williams; Editing by Alastair Macdonald