SINGAPORE - US Defense Secretary Robert Gates on Sunday cautioned Turkey against sending troops into northern Iraq, as it has threatened, to hunt down Kurdish rebels it accuses of carrying out terrorist raids inside Turkey.

US Secretary of Defense Robert Gates, right, talks with Australian Defense Minister Brendan Nelson, second right, as Chairman of the Joint Chief of Staff Gen. Peter Pace, second right, looks on at the start of their bilateral meeting during the 6th IISS Asian Security Summit in Singapore, Sunday, June 3, 2007. [AP]

"We hope there would not be a unilateral military action across the border into Iraq," Gates told a news conference after meetings here with Asian government officials. Turkey and Iraq were not represented.

Gates said he sympathized with the Turks' concern about cross-border raids by Kurdish rebels.

"The Turks have a genuine concern with Kurdish terrorism that takes place on Turkish soil," he said. "So one can understand their frustration and unhappiness over this. Several hundred Turks lose their lives each year, and we have been working with the Turks to try to help them get control of this problem on Turkish soil."

Tensions have heightened in recent weeks in northern Iraq as Turkey has built up its military forces on Iraq's border, a move clearly meant to pressure Iraq to rein in the rebels of the Kurdistan Workers' Party, or PKK, separatists who launch raids into southeast Turkey's Kurdish region from hideouts in Iraq.

Turkey's political and military leaders have been debating whether to try to root out those bases, and perhaps set up a buffer zone across the frontier as the Turkish army has done in the past. Turkey's military chief said Thursday the army was ready and only awaiting orders for a cross-border offensive.

Iraqi Prime Minister Nouri al-Maliki on Saturday urged Turkey not to stage a new incursion, saying his government will not allow the relatively peaceful area of northern Iraq to be turned into a battleground.

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

At the Singapore news conference Gates was asked about a reported U.S. naval bombardment on Friday of terrorist targets in northern Somalia.

"That's possibly an ongoing operation," he said, adding that as a result he would not comment on it.

Gates was in Singapore to attend an international security conference known as the Shangri-la Dialogue, where he reassured Asian nations that the United States remains committed to being a Pacific power and is not distracted by the Iraq war.

He said he did not ask any Asian government representatives to make new commitments to help in Iraq, but he did discuss with them at length the prospect of providing more assistance in Afghanistan. He said some countries, which he did not name, told him they were open to considering new commitments in Afghanistan.