Turkey is understood to be planning to send tens of thousands of soldiers into northern Iraq if the US attacks through the north.
Senior intelligence and military sources say the mission would be aimed at preventing a Kurdish state and stopping a possible flood of refugees.
About 4,000 Turkish troops, including engineers, have already been sent to the rugged, mountainous border region.
Washington has apparently asked for Turkey's permission to allow thousands of US soldiers through the country into Iraq if there is a war.
Turkish military officials have said that if there is an attack through the north, Turkey plans on sending its own soldiers into the region.
The Hurriyet newspaper says that Turkey is planning to deploy between 65,000 to 70,0000 troops in northern Iraq if there is a US assault from the north.
A senior intelligence official says Turkey is concerned that if Iraq disintegrates, Iraqi Kurds could seize the northern cities of Mosul and Kirkuk.
Mosul is a key regional centre and Kirkuk is home to major oil fields. Control of those cities would make the Kurds a significant regional power.
It's likely that Turkish soldiers in northern Iraq would secure the area, but would not take part in fighting against Iraqi troops. PA