"Actionable intelligence is something that we can provide," said White House spokeswoman Dana Perino, who referred reporters to US-led forces in Iraq for any details on help for the Turkish military.

Meanwhile the US State Department said it was hunting for a diplomatic resolution to tensions on Turkey's border with Iraq, after a new report raised the possibility of US-Turkish strikes on Kurdish rebels.

"We're working to resolve diplomatically what is a very difficult problem," department spokesman Sean McCormack told reporters, adding: "We do not believe that unilateral Turkish actions are the way to resolve this."

In a telephone call Monday with his Turkish counterpart Abdullah Gul, US President George W. Bush had offered support for Turkish efforts to counter deadly attacks by the PKK.

US officials have refused to elaborate on the nature of the cooperation, but the Chicago Tribune reported Tuesday that Bush had told Gul that US officials were seriously looking into options beyond diplomacy.

US officials have considered launching cruise missile against PKK targets, but air strikes using manned aircraft were an easier option, one unidentified official told the Tribune.

McCormack reaffirmed that authorities in Baghdad and Iraq's Kurdish north should also do more against the PKK, "regardless of their ethnic ties," and that "we should exhaust all diplomatic avenues."

"I am not aware of any American support for an airstrike," said Perino.

Bush urged Iraqi Prime Minister Nuri al-Maliki and Gul in separate telephone calls on Monday "to exercise restraint, for them to communicate and to cooperate because we do not want to see additional violence in that region," she said.

A possible joint operation was raised by Turkish Prime Minister Recep Tayyip Erdogan as he flew to Britain on Monday.

"We may conduct a joint operation with the United States against the PKK in northern Iraq ... We expect to work jointly, just as we do in Afghanistan," Erdogan told reporters on the plane.

Erdogan said he had received a signal that Washington might become involved during a telephone conversation with US Secretary of State Condoleezza Rice on Sunday.

"She was worried. I saw she was in favor of a joint operation," Erdogan said. "She asked for a few days' time and said she would come back to us."

Erdogan has threatened military action in northern Iraq unless Baghdad clamps down on PKK bases there and turns over the rebel leaders that Ankara accuses of masterminding cross-border attacks on its military.

McCormack also welcomed Maliki's order to close PKK offices, saying "it's a start" but calling anew for concrete action from Iraqi authorities to prevent PKK attacks and ultimately, "to dismantle and eliminate" the rebel group.