To catch a snake, use your enemy's hand.- Persian proverb

Last week's U.S. military re port alleging Iran is now giving weapons to Iraqi Sunni insurgents may seem downright illogical next to earlier claims that Tehran was arming Iraq's Shia militias.

It's not. Far from it.

While a risky strategy, Tehran's willingness to arm both their Shia allies and Sunni foes in Iraq could pay big dividends for the ascendant and ambitious Islamic Republic - at our expense.

In fairness, not everyone buys into the U.S. military's latest finger-pointing at Iran. Some are reasonably skeptical, saying the initial intelligence analysis could be half-baked.

Pieces of the puzzle do seem to be missing. For instance, the owner of the weapons cache that included some Iranian arms found in the Sunni-majority Baghdad neighborhood was never identified.

Moreover, the overarching conclusion about Iranian complicity is staked on separate intel provided by unidentified detainees, who claim Tehran is aiding Sunni insurgents. That info could be shaky, too.

Plus, the insurgents could've bought the arms on the international black market. Syria - an Iranian ally - could be the supplier. Or corrupt Iranian officials - looking to make a quick, easy buck - could've sold them to the insurgents.

Naturally, Iran denies any involvement.

But let's assume that the witch's brew of Iranian weapons (e.g., mortar rounds) found in a Sunni neighborhood - added to the detainee info - makes for a credible case against Tehran.

What accounts for Iran's action?

Although seemingly as incompatible as oil and water, the Sunni insurgents could help Shia Iran advance important strategic objectives in Iraq.

Continued Sunni attacks - aided by Iranian weapons - will keep the United States sufficiently distracted so as to hinder the possibility of Washington's dealing with Iran politically, much less militarily.

Plus, continued Sunni violence (again, supported by Iran) will only add to the possibility that the United States will defeat itself in Iraq by opting for a politically motivated withdrawal in Washington.

Sure, the Sunnis will use Iranian weapons to kill some Iraqi Shia, but what are a few Iraqi lives in the pursuit of clearing away the biggest hurdle to Iran's quest for Middle Eastern dominance - the United States?

Moreover, while Iran has no interest in complete chaos, a tolerable level of instability fomented by Iranian-aided Sunni and Shia - in a country that for many years was its greatest threat - would be welcomed by Tehran's sinister strategists.

The last thing Iran wants - ever again - is a strong, unified Iraq. Iranian President Mahmoud Ahmadinejad, a veteran of the 1980-88 Iran-Iraq War, remembers well the carnage, including the loss of 300,000 Iranian lives at Iraqi hands.

On top of that, Iran has no desire to see real freedom and democracy blossom in Iraq. Talk about an ideological threat to the repressive Iranian regime!

Tehran is already struggling to keep the lid on a simmering pot of social discontent; it doesn't need a "bad" political example right next door, turning up the heat that might push dissent to the boiling point.

Working both ends (that is, the Sunni and Shia) against the middle (that is, the Iraqi central government) will surely stifle Iraq's development toward a stable, fully-fledged democracy.

None of Iran's machinations should surprise us. Iran likes to get others to do its dirty work. Fighting by proxy is its M.O. That's why it's been such an active state sponsor of terrorism.

Just look at Hezbollah's role as Iran's cat's-paw. In 1983, Hezbollah killed 241 U.S. Marines in Beirut. Last summer, it fired some 3,000 rockets into Israel. Today, it's trying to topple the Lebanese government.

As with Hezbollah, using such surrogates as the Shia militias and Sunni insurgents to protect and advance its interests in Iraq is just another pernicious example of how Iran operates internationally.

Now, this isn't to say that Iran is behind all the problems in Iraq. There are real problems that are uniquely Iraqi. But Iran appears to increasingly have a hand in preventing the establishment of stability in Iraq.

Indeed, Tehran could be supporting other evildoers in Iraq, too - even al Qaeda. And considering the recent news of disagreements between al Qaeda and Sunni insurgents in Iraq, it's certainly possible Iran will aid al Qaeda, too.

Peter Brookes is a senior fellow at The Heritage Foundation and the author of "A Devil's Triangle: Terrorism, WMD and Rogue States."