It's impossible to say whether the U.S. will attack Iran before George W. Bush leaves office in 17 months' time, because nobody in the White House knows yet either.
But the most alarming sign is the news that the Bush administration is about to brand Iran's Islamic Revolutionary Guard Corps a "terrorist organization."
This is a highly provocative step, for the IRGC is not a bunch of fanatical freelances. It's a 125,000-strong official arm of the Iranian state, parallel to the regular armed forces but more ideologically motivated and presumably more loyal to the ruling clerics.
Declaring the Revolutionary Guards a terrorist organization isn't just a way for the U.S. government to vilify Iran as a terrorist state.
It's one of the key policy disputes between those in the administration, notably Secretary of State Condoleezza Rice and Defense Secretary Robert Gates, who think an attack on Iran would be unwise, and those around the vice-president, Dick Cheney, who think it is essential.
Almost everybody in the Bush administration believes Iran is seeking nuclear weapons in order to dominate the region and attack Israel. (Others are less certain.) The war party, led by Cheney, also believes that the clerical regime in Iran would collapse at the first hard push, since ordinary Iranians thirst for U.S.-style democracy - and that the attack must be made while Bush is still in office, since no successor will have the guts to do it.
What will happen if Cheney & Co. get their way? The Iranian regime would not collapse: President Mahmoud Ahmadinejad is now unpopular due to his mishandling of the economy, but patriotic Iranians would rally even around him if they were attacked by foreigners. What would collapse instead is the world's oil supply and the global economy.
Major-General Yahya Rahim Safavi, commander-in-chief of the Revolutionary Guards, explained how that would be accomplished in a speech on August 15 (though he made no direct reference to the U.S. threat).
"Our coast-to-sea missile systems can now reach the length and breadth of the Gulf and the Sea of Oman," he said, "and no warships can pass in the Gulf without being in range of our coast-to-sea missiles."
In other words, Iran can close the whole of the Gulf and its approaches to oil tanker traffic, and if the U.S. Navy dares to fight in these waters, it will lose.
Despite the huge disparity in military power between the U.S. and Iran, this is probably true. Overcommitted in Iraq and Afghanistan, the U.S. cannot come up with the huge number of extra troops that would be needed to invade and occupy a mountainous country of 75 million people. The U.S. can bomb Iran to its heart's content, hitting all those real and alleged nuclear facilities, but then it runs out of options - whereas Iran's options are very broad.
It could just stop exporting oil itself. Pulling only Iran's 3.5 million barrels per day off the market in its present state would send oil prices into the stratosphere. Or it could get tough and close down all oil tanker traffic that comes within range of those missiles - which would mean little or no oil from Iraq, Saudi Arabia or the smaller Gulf states either. That would mean global oil rationing and the end of the present economic era.
Can those missiles do all that? Yes, they can. The latest generation of sea-skimming missiles have mobile, easily concealed launchers, and they would come in very fast and low from anywhere along almost 2,000 kilometres of Iran's Gulf coast. Sink the first half-dozen tankers and insurance rates for voyages to the Gulf become prohibitive, even if you can find owners willing to risk their ships.
It's very doubtful that U.S. air strikes could find and destroy all the missile launchers (consider how badly the Israeli air force did in south Lebanon last summer), so Iran wins.
After a few months, the other great powers would find some way for the United States to back away from the confrontation and let the oil start flowing again, but the U.S. would suffer a far greater humiliation than it did in Vietnam, while Iran would emerge as the undisputed arbiter of the region.
Many, perhaps most, senior American generals and admirals know this and are privately opposed to a foredoomed attack. Cheney and his coterie don't know it, preferring to believe that Iranians would welcome their American attackers with glad cries and open arms. You know, like the Iraqis did. And Cheney seems to be winning the argument in the White House.
Gwynne Dyer is a London, England-based independent reporter whose columns appear in 45 countries. His latest book is The Mess They Made: The Middle East After Iraq.