Iraqi and Kurdish officials say 300 Turkish troops have crossed three kilometers into northern Iraq, but no immediate clashes were reported.
On a visit to Baghdad Tuesday, U.S. Secretary of State Condoleezza Rice said that the United States, Iraq and Turkey share a common goal in stopping rebels of the Kurdistan Workers Party, or PKK, in northern Iraq. But Rice cautioned against taking any action that could destabilize the north.
Rice also made clear that while the United States supports efforts to quash the PKK, which Washington considers a terrorist group, she said it was a "Turkish decision to act."
Turkey, which has about 100,000 Turkish troops massed on the Iraqi border, accuses PKK rebels of using bases in northern Iraq to carry out attacks in southeastern Turkey.
Tuesday's Washington Post quotes unnamed Pentagon officials as saying the United States is providing Turkey with real-time intelligence that has helped the Turkish military target the rebels in a series of attacks this month.
The officials say U.S. military personnel have created a center for sharing intelligence in Ankara.
Meanwhile, the United Nations refugee agency (UNHCR) says the Turkish bombardment in northern Iraq has forced 1,800 people to leave their homes.
Some information for this report was provided by AFP, AP and Reuters.