The Pentagon has been studying exit routes, in particular the borderwithJordan, butBabacansaidus forces could cross intoTurkey and use the airbase at Incirlik.
If, for instance, they really do close down IncirlikAir Force Base, we're going to be logistically blind in the north, and it would be extremely difficult for us to re-supply and to coordinate air strikes.
The more Turkey gets involved, the more comfortable the Americans feel about using Incirlik, the airbase from where they, Britain and Turkey enforce a no-fly zone over northern Iraq.