The confusion among the White House, Pentagon and our military in Baghdad last week over the presence of Iranian weapons in Iraq - and whom to finger for sending them there - was, let's just say, a bit awkward for the administration.

In fact, it took almost the entire week to set the record straight.

But in the end, there seems to be three things there is no question about: Iranian weapons are present in Iraq today, and they are killing U.S., Coalition and Iraqi forces. And something has to be done about it - ASAP!

The odyssey started in Baghdad over a week ago when U.S. officials briefed reporters on Iranian arms in Iraq, concluding that the "highest levels of the Iranian government" were orchestrating the flow of weapons into the country.

Then the chairman of the Joint Chiefs of Staff, Marine Gen. Peter Pace, on the road in Asia, sparked controversy, saying he wasn't ready to conclude that Iran's government was directing the arms supply to Shia militias, such as the Mahdi Army or Badr Corps.

Putting a finer point on it, President Bush then asserted Iranian arms were killing U.S. GIs in Iraq, blaming the mysterious Quds force. But he couldn't be certain exactly who in Iran was responsible for the arms smuggling that the military claims killed 170 Americans and wounded 650 in a year.

Cutting to the chase, Bush said: "What matters is that they're [Iranian weapons] there . . . What's worse: that the [Iranian] government knew - or that the government didn't know?"

(In a way, this isn't really news at all - the Brits have been reporting on possible Iranian arms in southern Iraq for nearly two years now, but the problem is getting worse.)

So how did Iranian weapons, such as deadly .50 caliber sniper rifles, armor-penetrating "EFP" (explosively formed penetrators used as roadside bombs), rocket-propelled grenades and shoulder-fired missiles, (the last two capable of downing helos), get into Iraqi hands?

• Possibility 1: Black market. The weapons could've been purchased off the international arms gray/black market by the Shia militias or could've been provided to them by other sympathetic Shia intermediaries in Iran or elsewhere.
• Possibility 2: Rogue elements. The Iranian Ministry of Intelligence and Security, the paramilitary Iranian Revolutionary Guard Corps (IRGC) or its shadowy Quds force could be involved in rogue operations to supply these weapons.
• Possibility 3: The Iranian government. The weapons shipments may have been authorized by Iranian President Mahmoud Ahmadinejad or thereal power in Iran, Supreme Leader Ayatollah Ali Khamenei. (The IRGC/Quds report to Khamenei.)

So what can be done?

First, the president rightfully sent a not-so-veiled warning to Tehran, saying: "I'm going to do something about it, pure and simple." Naturally, this led some to the breathless conclusion that the bombing of Tehran starts in five minutes. Not likely.

But the prez did put Iran on notice that we know it's involved, leaving Tehran to think the worst. If it's smart, Tehran will move to curtail the arms shipments - whether it's directly behind them or not. But don't hold your breath.

Moreover, shedding light on the subject might bring additional international pressure on Iran, which is already wincing from the U.N. sanctions against its banks over its defiance on its nuclear program.

Of course, pressing the intelligence offensive is critical, too. Interdicting shipments at the border, seizing arms caches and collapsing sites in Iraq, where such weapons as EFP are sometimes assembled from Iranian kits, are key.

And while the smugglers are secondary to stopping the weapons' use, cracking down on Iranian intelligence/security personnel inside Iraq, especially the fanatical Quds forces that are training, funding, directing and arming Shia militias, must also be a priority.

The administration has broadly pointed a finger in the direction of Iran but (rightly) has held off on laying the blame at someone's feet until there is more damning information. Some pieces of the puzzle are simply missing.

The president was right to be slow on the draw in indicting Tehran's senior leaders - though there is little doubt in any clear-thinking person's mind that these arms transfers are Iranian national policy, despite Tehran's official denials.

The administration is being careful due to lingering questions and doubts about the sturdiness of U.S. intelligence in general, arising from the Iraq WMD intel failure.

The White House undoubtedly wants an iron-clad case this time, supported by solid evidence. Only a smartly constructed picture of the Iranian threat is going to convince others of its seriousness.

Peter Brookes is a columnist forThe New York Post, a Heritage Foundation senior fellow and author of "A Devil's Triangle: Terrorism, WMD and Rogue States."