If you listen closely, there are eerie similarities between the sabre rattling now being heard over Iran and that cacophony of war-hawk voices that helped propel the U.S. into the Iraq war in 2003.

This time, the raised voices revolve more around the need to support Israel, should it attack Iran's supposed nuclear weapons sites, and they are being heard more urgently in the Republican leadership debates and by the familiar hardliners in Washington's neo-conservative circles.

Some of the same over-the-top rhetoric is back in play. Newt Gingrich, who currently leads the Republican presidential field, claimed recently that the U.S. "could break Iran in a year."

Where have we heard that kind of bluster before?

But there are important differences as well from the Bush/Cheney/Rumsfeld period. For one, military action is a much harder sell these days given the widespread war-weariness that has followed the grinding combat in Iraq and Afghanistan.

While it's true some polls suggest that roughly half of Americans would support military action in Iran, should sanctions fail, overall large numbers still favour diplomacy as the first option.

Even that big rattling noise from the right today does not equate to the war fever that possessed Washington eight years ago.

'A terrible price'

When it comes to assessing America's war rhetoric we should keep in mind that there are now significant brakes on any headlong rush into yet another conflict in a far-off Muslim land.

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An Iranian woman walks past an anti-U.S. mural on the wall of the former American embassy in Tehran in October 2011. (Reuters)

Americans are now more politically divided on all issues and the one that dominates attention is the economic crisis, not Iran.

Even the conservative agenda in the U.S. is divided as many in the Tea Party movement favour a new form of isolationism and reject new adventures abroad.

Most importantly, few Americans seem to share Gingrich's rosy optimism over America's ability to easily crumble unpopular governments abroad.

Iraq and Afghanistan taught bitter lessons and today the White House and Pentagon are not dominated by the more free-wheeling war hawks of the Sept. 11 period.

Note for example the extraordinary warnings from U.S. Defence Secretary Leon Panetta last week when he told a forum in Washington that any attack on Iran would risk "unintended consequences," including an escalation that could "consume the Middle East in confrontation and conflict that we would regret.

"The United States would obviously be blamed and we could possibly be the target of retaliation from Iran, striking our ships, striking our military bases."

What's more, he went on, any U.S. attack would only bolster the Iranian regime, in the struggle with its internal critics, while at the same time disrupting the struggling economies of the U.S. and Europe.

Panetta's bluntness suggests the U.S. is being very firm in warning the Israelis to resist trying to take out Iranian targets at this time.

These risks have been raised as well by prominent Israelis, including former Mossad chief Meir Dagan who recently warned Israel would "pay a terrible, unbearable price" for such an attack, including retaliation in the form of thousands of missiles from Iran, Hamas, Hezbollah and perhaps even Syria.

Covert war

Of course, the absence of an imminent aerial attack on Iran by Israel or the U.S. does not mean we're in a period of peace.

Rather, what we are seeing is a sinister covert war that involves kidnappings and assassinations of scientists, the possible use of computer viruses to destroy information networks, and mysterious explosions at Iranian nuclear sites, all of which seem to be escalating.

It's an odd, unacknowledged war within Iran where no one claims responsibility but no one bothers to deny responsibility very convincingly either.

Last year, two leading nuclear physicists were killed and the head of the Iranian Atomic Energy Organization was wounded by car-bomb attacks inside Iran, attacks Teheran blamed on Israeli and U.S. operatives.

Months later, Iran's nuclear program was sabotaged and put back at least a year by the Stuxnet computer virus.

The virus, widely believed to have been created by a joint Israeli-U.S. intelligence operation, made secret adjustments to centrifuges at Iran's uranium enrichment site.

Then, on Nov. 12 this year, an enormous explosion virtually obliterated a top secret base near Teheran that was being used for developing long-range missiles.

The blast killed the head of Iran's missile program and 17 others, including key experts in the field, and was blamed on an accident, although there are strong suspicions in intelligence circles that sabotage was again involved.

Just two weeks later, another large explosion damaged the key uranium enrichment plant at Isfahan. Again there was no clear explanation for the blast and no one took credit. But two giant blasts to Israel's great benefit does seem an odd coincidence.

Tit for tat

Indeed, some found it hard not to gloat. Dan Meridor, Israel's minister for intelligence and atomic matters, told an Israel radio station that espionage had definitely set back Iran's nuclear program: "There are countries that impose economic sanctions and there are countries who act in other ways."

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Two members of Iran's Revolutionary Guard stand behind a U.S. spy drone that Iran says it brought down electronically over its northeastern border with Afghanistan in November 2011. The banner behind reads Down with the U.S., down with Israel, and down with Britain.

As usual in the Middle East, intelligence services use proxies on the ground to do their dirty work.

The Mossad and CIA are widely reported to be working with Iranian exiles of the MKO (sometimes called MEK) — the military wing of the National Council of Resistance, which has strong links to U.S. conservative groups favouring action against Iran.

But this is not a one-sided conflict. For years Iran has been directing Shia militia in the roadside bombings that killed and maimed American troops in Iraq, and it is a strong backer of Hamas and Hezbollah in their clashes with Israel.

More recently, in October, Iran was accused of masterminding a bizarre plot to kill the Saudi Arabian ambassador in Washington and blow up his embassy.

Iran denies it all, and the details are still murky, as they are as well with the Iranian demonstrators who stormed the British Embassy in Teheran last week shouting "Death to Britain."

The incident caused a huge breach in diplomatic relations and more calls for international sanctions against Iran. But here, too, nothing is clear and it's not known which faction in Iran's quarrelsome inner circle gave the go-ahead.

The future of conflict?

Can today's wars be fought entirely by stealth? Certainly there is no sign this mysterious and opaque war will end anytime soon.

A leading scholar of Iran, Patrick Clawson at the Washington Institute for Near East Policy, believes these campaigns of assassinations and cyber-war and only vaguely acknowledged sabotage mark a new form of conflict in our world.

As he puts it, "It looks like the 21st-century form of war."

If so, if this really is the future of conflict, it worries scientists and generals alike.

For if it's never made clear who is doing what, then how do we even begin to seek control of events?

Mark Hobbs, a nuclear expert at the Carnegie Endowment, warns that this mysterious mix of assassinations and bombings risks a descent into chaos.

"Some of the concern in the scientific community," he says, "is that in going down this route we're unleashing forces we cannot control."

I don't know about you, but it is starting to feel like we are well down that route already.