Quite a dangerous situation is shaping up on the border between Turkey and Iraq. Our Eli Lake, who has been way ahead of the other papers, reported yesterday that as many as a quarter of a million Turkish troops — twice as many as the number of GIs we have in Iraq — are massing on the border. Mr. Lake quoted the top Turkish general, Yasar Buyukanit, as saying that his soldiers were awaiting instructions to attack in northern Iraq the havens whence the Kurdistan Worker’s Party, or PKK, are infiltrating into America’s ally.

No doubt there will be some temptation to say to the Turks that if they had been more supportive of the Coalition of the Willing in the early stages of the Battle of Iraq, they would find greater sympathy in the current situation. But no one need have any sympathy for the PKK, a Marxist type revolutionary movement. And Mr. Lake quoted one of our state department spokesmen, David Foley, as saying that Washington was in “close communication” with the Turks, the Iraqis and the Kurds in hopes of resolving the issues through the “existing tripartite process.”

The fact is that a war between the Turks and the Kurds would be a tragedy. It would be tragic for the Turks, for the Kurds, for America, and for all with a stake in the world war against Islamist fascism. The Turks and America, moreover, are bound to one another and to the Europeans by the North Atlantic Treaty, which holds, among other things, that an attack on one member of the alliance must be treated as an attack on all. The Turks have been allowing us to use their air bases in Incirlik, a key position should America ever need to bomb the centrifuge cascades in Natanz, Iran.

In Irbil and Suliminiya, a Kurdistan Regional Government has been providing our GIs with intelligence on the machinations of Al Qaeda inspired terrorists. Kurdish forces in 2003 helped locate Saddam Hussein before General Odierno’s men rounded up the war criminal. Of the major ethnic factions in Iraq, the Kurds have been the most patient, never raising a finger against the elected government they helped create after the fall of Saddam.

It would not be too much to say that one of the things that has underlain this war is a recognition — brought home before the invasion by the brilliant reporting from Kurdistan by Jeffrey Goldberg of the New Yorker — that the crimes against the Kurds are crimes that could not be allowed to stand. Yet, when it comes to the relations between Turkey and the Kurds, Iraq’s Kurdish president, Jalal Talabani, is careful to call them “brothers,” because as he says, “while you can choose your friends, you cannot choose your brothers.” This is a polite joke that covers generations of bitter animosity.

Keeping these two allies in the wider war from going to war themselves is a far more logical priority for our State Department than focusing on the pursuit of Iran and the effort to revive the Oslo process. We don’t need to remind our friends in Ankara of the valorous efforts of the Kurdish militias against the Al Qaeda inspired Ansar al Sunna, now sheltered in Iran. Nor should it be necessary even to ask our Kurdish friends to expand their security efforts beyond the Qandil Mountains to where the Turks believe the PKK has expanded its training camps. President Bush, who is in Europe now for the Group of Eight, has an opportunity to exert the kind of leadership that is at a premium in situation that couldn’t be more dangerous.