A couple of months ago, pundits were predicting that a U.S. attack on Iran was imminent.

The buzz was propelled by President Bush’s tough talk about Iran in a Jan. 10 speech on Iraq, by the dispatch of more U.S. ships to the Persian Gulf, and by repeated American claims that Iran was helping radical Shiites kill U.S. troops in Iraq. Speculation was intense about potential U.S. (or Israeli) bombing raids on Iran’s suspect nuclear energy program.

But an amazing shift in tone – among U.S. officials and Iran experts – has occurred in the last couple of months. I heard it at a high-powered conference on Iran run by the Rand Corp. in Washington organized last week to air the issue of possible war with Iran.

None of the many speakers, from hawk to dove, thought that U.S. military action would end Iran’s nuclear program. None thought an attack on Iran would end the regime of the ayatollahs. All thought an attack would worsen America’s situation in Iraq and embroil the United States in another endless conflict. In other words, even political hawks now grasp that bombing Iran is a bad idea.

Why so?

Danielle Pletka, vice president of the conservative American Enterprise Institute, said: “Military options (toward Iran) are not satisfactory. They won’t end the (nuclear) program and they will have consequences. The regime will lash out at us.”

Michael Eisenstadt, the director for military and security studies at the conservative Washington Institute for Near East Policy, was equally cautious. “I thought WMD was a slam dunk before the Iraq war,” he said, “but I don’t assume anything any more after Saddam Hussein.” He added that the United States should not give up on the diplomatic option with Iran.

What has crimped the idea of bombing Iran? David Ochmanek, a senior defense analyst for Rand (known for its tough strategic reports), laid out the negatives: a U.S. attack on Iranian sites, far from weakening the regime, would cause it to close ranks (and strengthen the hand of radical President Mahmoud Ahmadinejad, who faces criticism at home for economic and diplomatic blunders). Iran would ratchet up pressure on U.S. troops in Iraq (which is minimal now, despite administration rhetoric). Tehran might attack oil and gas ships in the Gulf. A U.S. attack would also ensure that Iran’s leaders would redouble their efforts to get a bomb – and would boost jihadi movements worldwide.

In other words, bombing Iran, far from curtailing Iran’s potential nuclear threat, would make the threat more real.

So, if the down side is so obvious, why was the White House rattling sabers in January? And why is the tone being tempered now?

No doubt the White House was trying to keep the pressure on Tehran by holding out the military option. But the downside of that option has become ever clearer in recent months.

As more troops deploy to Iraq, the U.S. military is overextended. Marine Gen. Peter Pace, chairman of the Joint Chiefs of Staff, raised eyebrows in February when he insisted he had no information indicating Iran’s government was directing lethal weapons to Shiite militias in Iraq, even though administration officials were implying the opposite. Clearly, our military is wary of getting embroiled in another open-ended conflict.

So the White House has been talking up the diplomatic option, joining regional talks on Iraq this month that open a possibility of direct dialogue with Iran. Undersecretary of State Nicholas Burns, Condoleezza Rice’s talented point man on Iran, said at the Rand conference: “We are firmly focused … on a diplomatic solution.”

Can we then assume that the chances of war with Iran are zilch?

Perhaps. But if tensions remain high, incidents between Iranians and coalitions forces could escalate inside Iraq or in the Gulf. A good example, is the Iranian seizure last week of 15 British Navy personnel in disputed Gulf waters. And if things worsen in Iraq, might the White House decide to divert attention to Iran? Probably not, but …

This lingering mistrust (is Dick Cheney still making policy?) is why I wish House Democrats had not stripped their Iraq funding bill of a provision requiring Bush to seek congressional approval before launching war on Iran. I’m opposed to Democratic efforts to set timetables for U.S. troops to quit Iraq, because I think timetables should be part of a broader regional diplomatic process. Yet a war with Iran would be so disastrous that Democrats should have laid out a clear legislative marker.

The White House can squeeze Iran to change behavior by use of United Nations sanctions and by international economic pressure and more creative diplomacy. But it’s time to dump the transparent illusion that bombing could work.