Erdogan said: "Our expectations have been relayed to the opposite side. We have to achieve results. It would not be right to spell out a deadline."

Erdogan did not rule out a cross-border Turkish operation against the separatists.

"The target is to achieve results. Our patience has run out. The necessary steps will be taken when needed."

The Turkish prime minister said the technical, military and diplomatic aspects of a possible cross-border incursion were being evaluated.

The US opposes Turkish military action in Iraq, fearing it could destabilise the calmest part of the war-torn country.

Ankara has repeatedly expressed its disappointment with Washington for what it says is a failure to crack down on Kurdish rebels who take refuge in northern Iraq and frequently attack soldiers and government targets in Turkey.

The Kurdish rebel group, the PKK, has been fighting for autonomy since 1984. Tens of thousands of people have died. The rebel group is considered a terrorist organization by the United States and the European Union.