"We have been working hard since November 5 to follow up the conversation between President (George W.) Bush and Prime Minister Erdogan to increase cooperation among Turkey, Iraq and the United States to counter the PKK terrorist threat," White House National Security Council spokesman Gordon Johndroe said in a statement.

Earlier Turkey said it inflicted "heavy losses" with airstrikes and artillery against a group of "50 to 60 terrorists ... inside Iraq's borders" in the mountainous region southeast of the Turkish town of Cukurca in Hakkari province.

US State Department spokesman Edgar Vasquez declined to confirm the reports of the Turkish attack.

"I can't confirm (those reports)," he told AFP.

"We're encouraging Turkey and Iraq to work together," he added, referring to previous US calls for Ankara to hold talks with Baghdad on the issue.

In Baghdad the US military said it had no reports of Turkish military operations in northern Iraq.

"We have nothing; we have no reports like that at all," spokesman Major Winfield Danielson told AFP.

Danielson added the US military in Baghdad wouldn't be expected to be the primary source of information about any Turkish military activity in Iraq's Kurdish region.

"The Iraqi government and the Kurdistan Regional Government would be the first to know about something like this. Kurdistan is an autonomous region," he said.