Reports are extremely murky right now, but it appears that the Turkish Army has crossed the Iraqi border into the autonomous region of Kurdistan. While the AP reports that "thousands" of Turkish troops deployed into Kurdistan, an anonymous Turkish official insisted to Reuters that the move "cannot be called a cross-border operation, it is a limited operation."

Whatever's happening, tensions have been at a boil for the last week, as the Turks have made noises about taking military action after a June 1 incident in which Kurdish forces in the city of Sulaymaniya allegedly harassed plainclothes Turkish soldiers. The next day, however, the U.S. military command turned over formal control of security to the Kurdistan Regional Government. The KRG was largely responsible for security before -- as I learned on a 2006 trip to Kurdistan, there were very few U.S. troops in the comparatively placed region even before Saturday's formal handover -- but the handover put U.S. forces firmly in a supporting role:

Coalition forces will resume their role in the region as support when needed.

“It is important to understand that Coalition forces will always be here to support the Government of Iraq,” said U.S. Air Force Maj. Gen. Kurt A. Cichowski, deputy chief of staff, strategy, plans and assessment for MNF-I.

While Coalition forces support the KRG, they have also contributed $436 million during the war for reconstruction efforts in the area.

“Today’s event is symbolic because the people of these provinces have been taking the lead and demonstrating progress for quite some time,” said [Major General Benjamin] Mixon.

It's by no means clear what, if any, effect the handover had on Turkish decision-making. But it may be that the Turkish general staff, which has been acutely concerned with terrorism against Turks by the Kurdistan Workers' Party (PKK), interpreted the move as a sign that the U.S. was scaling down its commitment in the Kurdish north of Iraq. At the very least, invading Turkish forces wouldn't face a U.S. military command charged with holding and defending the area.

Regardless, any move by the Turks into Iraqi Kurdistan severely complicates the U.S.'s position: a NATO ally is fighting the U.S.'s best friends in Iraq. On Sunday, Defense Secretary Gates was asked about a possible Turkish action against the Kurds:

Q: Mr. Secretary, there have been growing rumblings over the last couple of days about the possibility of a Turkish invasion in northern Iraq to go after the PKK. I'm wondering whether you see that as a real possibility, and if this were to happen, what would it mean to the overall effort to stabilize Iraq and to keep it intact? SEC. GATES: Well, I think, first of all, the Turks have a genuine concern with Kurdish terrorism that takes place in Turkish -- on Turkish soil, and so it's -- one can understand their frustration and unhappiness over this. Several hundred Turks lose their lives each year, and we have been working with the Turks to try and help them get control of this problem on Turkish soil.

I think our view would be that if -- we would prefer that we continue to work this problem with them to try to safeguard Turkey and would hope that there would not be a unilateral military action across the border into Iraq.

Again, it's not clear what exactly is going on in northern Iraq, but any Turkish action after Gates's statement surely represents as a decision to flout the United States.