Chatham House, noting that the Iraqi government is cautious about confronting the Kurdistan Workers' Party (PKK), added that Kurdish nationalism is experiencing a popular and "political renaissance" in the whole region.

"The PKK is a well-motivated force that enjoys local support and the protection afforded by the inaccessible terrain of the border regions," it said in a report, released a day after Turkish troops entered northern Iraq.

"Turkey can probably never defeat the PKK and any further incursions across the border are likely to be futile," it added.

Tuesday's Turkish incursion to flush out separatist Kurdish rebels was the first reported ground incursion inside Iraq since tension between Ankara and Baghdad erupted over the issue in October.

The London think-tank said the Iraqi government "is reluctant to tackle the PKK because of the military risk involved.

"Even if it managed to flush them from the mountains, this might leave the door open for radical Islamists to turn the region into their own Tora Bora-style stronghold," it noted.

Chatham House noted that Turkey's recent air strikes on PKK bases in Iraq demonstrate the growing significance of Kurdish politics in the four states with major Kurdish populations: Turkey, Syria, Iraq and Iran.

"Kurds are experiencing a political renaissance in the Middle East," it said.

Tension between Iraq and Turkey has been high since October 21 when the PKK ambushed a Turkish military patrol, killing 12 soldiers.

Since then Ankara has been threatening to launch a major military incursion to flush out PKK fighters hiding out in Iraq's mountainous north.

But lobbying by the United States and appeals by Baghdad stopped them from staging a full-fledged incursion.