Turkey could send troops into Iraq any day now. It's massing ground forces on its southeastern border for a possible strike against the terrorist/separatist group the Kurdistan Workers' Party (PKK).

Turkish special ops are likely already on the ground in Iraq.

This is the last thing we - or the Iraqis - need. Preventing it must be a top priority of America, Iraq and Europe.

The Kurdish area is the most stable and pro-American part of Iraq; neither Washington nor Baghdad can afford to have it become a new item on the "problem" list.

The Turks wouldn't go in unopposed, either. Besides the PKK, Iraqi Kurds have promised to resist any Turkish incursion into Iraq.

The Kurdish Peshmerga militia troops - just recently integrated into the Iraqi national army - are no slouches, meaning plenty of bloodshed in a donnybrook with the Turks. Baghdad has also warned against any Turkish action. It needs Kurdish/Iraqi troops focused on fighting its bad guys: al Qaeda, foreign jihadists and other insurgents.

Fighting between Turks and Kurds in Iraq could also spread to Turkey's large Kurdish population of about 15 million. Even an accidental engagement with U.S. troops would damage U.S.-Turkish relations, including Turkish air-base access for supplying U.S. forces in Iraq and Ankara's support to Coalition efforts in Afghanistan.

All that said, the Turks have good cause for being agitated. The PKK, numbering 4,000 in Iraq and 2,000 in Turkey, is a vicious bunch. Since 1984, when it began pushing for an independent homeland in southeastern Turkey, over 30,000 have been killed in insurgent, terrorist and Turkish force operations; the PKK killed 600 in 2006 alone.

It stepped up attacks recently, killing 20 soldiers and civilians in the last two weeks. A suicide bombing in Ankara in late May killed six and wounded more than 100. The Turks blame the PKK; the Kurdish rebels deny responsibility.

Turkish Prime Minister Recep Tayyip Erdogan noted: "Our patience has run out . . . necessary steps will be taken when needed." The Turkish chief of the General Staff said the army is ready - all he needs is the "go-ahead." The Turkish public seems up for a strike, too.

An incursion into Iraq against the PKK wouldn't be unprecedented. Turkish forces crossed the border a decade ago; they came close to doing so again last year after the PKK ended a self-imposed cease-fire.

But Turkey isn't entirely innocent here, either. Ankara has ruled the Kurds, 20 percent of Turkey's population, with a heavy hand. Kurdish autonomy across the border in Iraq hasn't gone unnoticed.

And then there's the issue of Turkish domestic politics. The current ruling political party, the AKP, has been down on its political luck lately. It might see a little jingoism in the form of military action as just the ticket to boost its flagging popularity before upcoming elections.

Still, it could all be a bluff - a warning. Turkey is fed up with the PKK and wants the United States (its NATO ally) and Iraq to do something about it. A military buildup sends a clear signal that Turkey wants - indeed, demands - action. In the mean time, maneuvers on the border could pacify the Turkish domestic audience.

But if the PKK attacks in Turkey continue as they have, Ankara may just give the army the dreaded green light.

That could mean a limited attack - targeting PKK strongholds in the Qandil mountains, using aircraft and helicopter gunships. Worse, Turk special ops could target Kurdish leaders they believe are turning a blind eye to the PKK. But that could escalate, too. Turkish ground troops might pour over the border, setting up a buffer zone in Iraqi territory along a portion of the 200-mile dividing line to prevent PKK infiltration into Turkey.

So what to do?

Call on the Turks to exercise restraint. Kick diplomacy into high gear, using all channels possible. Our current special envoy, Gen. Joseph Ralston (ret.), can use the uniform to appeal to the politically powerful Turkish military.

NATO can do some arm-twisting of its fellow alliance member, too. And the European Union should act - shutting down the numerous PKK networks there. (The European Union can also remind Turkey that good behavior would help its chances of membership, although interest in joining among Turks is waning.)

Iraq's leading Kurds need to do their share. President Bush's meeting last week with Iraqi President Jalal Talibani, an influential Kurd, could help move things off dead center. Fortunately, there's been some word out of the Kurdish Regional Government, leaning in the direction of a crackdown on the PPK. We need to see some action, not just words, on that front.

If all else fails, U.S. and Iraqi forces could move against the PKK - a group on the U.S. terrorist list - closing camps and ending cross-border raids into Turkey. Not ideal, but better than a showdown with Ankara.

More violence in Iraq, especially involving a major power and a strategic ally like Turkey, would make our challenges there even more difficult. A Turkish-PKK war in Iraq must be avoided at all costs.

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