"We think that those kinds of statements are really unhelpful and they certainly do not further the goal of greater Turkish-Iraqi cooperation," State Department spokesman Sean McCormack said in response to Barzani's remarks.

"We think that Iraqi leaders should focus on how they might work together closely with the Turkish government to further their mutual interests in a stable, secure Iraq," he said.

Mccormack also confirmed that Secretary of State Condoleezza Rice spoke with her Turkish counterpart, Abdullah Gul, over the weekend as the dispute with the Iraqis heated up.

Barzani, the head of the autonomous Kurdish region in northern Iraq, was quoted in a weekend interview threatening to interfere in Turkey's affairs if Ankara continued to oppose Kurdish claims on the oil-rich city of Kirkuk.

The future status of the northern Iraqi city is scheduled to be decided in a referendum before the end of this year. Turkey wants the vote postponed, arguing that thousands of Kurds have been moved into the city to change its demography.

Ankara worries that Kurdish control of Kirkuk and its vast oil reserves would embolden what it believes are Kurdish ambitions to break away from Baghdad.

Kurdish independence, it fears, could fuel the two-decade Kurdish separatist insurgency in adjoining southeast Turkey.

Tensions are already high between the two sides over Turkish accusations that Iraqi Kurds tolerate, and even support, thousands of armed Turkish Kurd rebels who have found refuge in the mountains of northern Iraq.

Ankara has threatened a cross-border operation into the region to crack down on the rebel camps if Baghdad and Washington fail to act against them.

Barzani's latest remarks sparked an angry response from Turkish Prime Minister Recep Tayyip Erdogan, who warned the Iraqi Kurds on Monday that hostility toward his country could result in a "very heavy cost" for them.

A senior Turkish diplomat told AFP that Gul conveyed Turkey's annoyance to Rice during their weekend telephone conversation.

According to McCormack, Rice sought to calm tensions and thanked Gul for his efforts to convene a meeting of Iraq's neighbors and major world powers next month to discuss ways to stabilize Iraq.

Washington had sought to have the meeting held in Istanbul, but Baghdad chose instead to organize the gathering in Egypt, reportedly in response to pressure from Iraqi Kurds.

Rice "expressed her support for Turkey's actions in rallying the neighbors to get together for the Iraq neighbors conference," he said.

McCormack also echoed Turkish concerns that the rebel Kurdish Workers' Party (PKK) could step up cross-border attacks into Turkey as warmer spring weather arrives.

Rice has named a retired US general, Joseph Ralston, as a special envoy working to lower tensions between the Turks and Iraqi Kurds.

"We're now coming up on the springtime, which is traditionally when the PKK goes on the offensive, crossing the border into Turkey. Nobody wants to see that," he said.