US Defense Secretary Robert Gates right, and General Peter Pace, US Chairman of the Joint Chiefs of Staff, in Singapore, 03 June 2007

Speaking to reporters Sunday in Singapore, where he is attending an Asian security conference, Gates said he sympathized with the Turks' concern over cross-border raids by Kurdish rebels.

But he cautioned Turkey against taking unilateral action across the border into Iraq, saying Washington wants to work with the Turks to help them get control of the problem of terrorism on Turkish soil.

"The Turks have a genuine concern with Kurdish terrorism that takes place on Turkish soil," said Gates. "And so, one can understand their frustration and unhappiness over this. Several hundred Turks lose their lives each year. We have been working with the Turks to try and help them get control of this problem on Turkish soil. Our view would be that we would prefer that we continue to work this problem with them to try and safeguard Turkey and would hope that there would not be a unilateral military action across the border into Iraq."

Tensions have been rising amid charges that Kurdistan Workers' Party (PKK) rebels have found sanctuary in Kurdish controlled areas of northern Iraq.

The Turkish army keeps a contingent of a few thousand soldiers in the mountainous border region to monitor the activities of Turkish Kurdish rebels holed up in bases in the area.

Turkey's military chief said Thursday the army was ready and only awaiting orders for a cross-border offensive.

In Irbil Saturday, Iraqi Prime Minister Nouri al-Maliki warned Turkey against conducting cross-border raids, saying he will not allow Iraq's largely peaceful Kurdish region to become a battleground.

Turkey accuses Iraqi Kurds, who once fought alongside the Turkish soldiers against the PKK in Iraq, of supporting the separatist rebels. Turkey also worries that the war in Iraq could lead to the country's disintegration and the creation of a Kurdish state in the north.