It's not clear how many Turkish troops have crossed into Iraq or how long they'll be there. The Turkish Prime MInister said the incursion would not affect normal Iraqis. Turkey accuses the PKK (Turkish separatists) of killing thousands of people in its violent struggle for Kurdish independence. The Prime Minister said he warned the US before the incursion and that the troops would return after they completed their mission. The White House confirmed it was informed of the incursion. A spokesman told Turkey to keep the incursion limited, but the US has provided Turkey with intelligence on the PKK, whom the US considers to be a terrorist organization. The ground operation marks an escalation. The US worries that Turkish troops could end up in a confrontation with Iraqi Kurds, whose government and fighters are key US allies in Iraq. Iraqi Kurdish officials have called for a diplomatic solution to the PKK problem but the US has accused those officials of failing to reign in PKK terrorists. This US official says all sides have an interest in keeping things in check.