"We recognize that the PKK is a serious problem and we're working closely with both the government of Iraq and the government of Turkey to resolve this," Pentagon spokesman Bryan Whitman said.

Whitman would not elaborate, Middle East Newsline reported. But diplomatic sources said the U.S. and Turkish militaries were examining joint operations against PKK bases in the Kandil mountains near the Turkish border. They said the operations would be conducted in coordination with the autonomous Kurdistan government.

"While detailed operational plans are necessarily concealed, the broad outlines have been presented to selected members of Congress as required by law," Novak said in a column. "U.S. Special Forces are to work with the Turkish Army to suppress the Kurds' guerrilla campaign."

Last week, Defense Undersecretary Eric Edelman told Congress of plans by Turkey and the United States for an operation that would decapitate the PKK leadership. Edelman told skeptical House and Senate members that Washington would deny any role in the invasion.

The sources said the United States has sought to prevent a Turkish military invasion of northern Iraq, which could lead to a war with the Kurdistan government and the destabilization of northern Iraq. They said an alternative was a Turkish-U.S. operation in cooperation with pro-U.S. Kurdish forces.

"The plans for any operation are not immediate," a diplomatic source said.