Turkish warplanes meanwhile bombed separatist Kurdistan Workers' Party (PKK) positions in northern Iraq and intensive fighting was reported on the ground near a major rebel base, Iraqi security sources said.

Despite Turkish refusal to give a timetable for a pullout, US Defence Secretary Robert Gates said after talks in Ankara he believed Turkish leaders got his message.

Speaking after meeting with Defence Minister Vecdi Gonul, Gates said the incursion, launched on February 21, should be "as short and precisely targeted as possible".

Gonul responded that "Turkey will remain in northern Iraq as long as necessary" and the troops will return home once PKK hideouts are destroyed.

"There is no need for us to stay there after we finish (off) the terrorist infrastructure... We have no intention to interfere in (Iraqi) domestic politics, no intention to occupy any area," he told reporters.

Gates had said Tuesday the offensive should last no longer than "a week or two" but Turkish army chief Yasar Buyukanit made it clear that Turkey would not be constrained by deadlines.

"A short time is a relative term. Sometimes this can mean one day and sometimes one year," he said after talks with Gates, adding that the United States has been fighting the Taliban in Afghanistan "for years."

Ankara says an estimated 4,000 rebels use northern Iraq as a base in their campaign for self-rule in Turkey's mainly Kurdish southeast; the conflict has claimed more than 37,000 lives since the PKK took up arms in 1984.

The United States, along with the European Union, lists the PKK as a terrorist group and has supported NATO ally Turkey by providing intelligence on PKK movements.

Gates played down suggestions the United States could cut off the intelligence supply if Turkey refuses to withdraw quickly.

"We have shared interests and I think those interests are probably not advanced by making threats or by threatening to cut intelligence," he said.

But Washington is concerned that the incursion could broaden into a wider conflict between Turkish forces and the Iraqi Kurds, who run the autonomous administration of northern Iraq and are staunch US supporters.

Turkey has long accused Iraqi Kurds of providing the PKK with safe haven and weapons, and warned them this week not to shelter rebels fleeing the fighting.

As Gates flew back to Washington, he told reporters on his plane he discussed no date for withdrawal in Ankara but "I think they got our message."

Pentagon press secretary Geoff Morrell added: "They made it clear they believe it is in their interest to accomplish this operation quickly. But they also wish to accomplish the objectives they set out to."

Gates, who also met with Prime Minister Recep Tayyip Erdogan and President Abdullah Gul, urged Ankara to back up military action with political and economic gestures to the sizeable Kurdish community to erode popular support for the rebels.

"That's the only way to isolate terrorism from the population and provide a long-term solution," he said.

Erdogan's government is already under pressure at home to improve Kurdish rights, tackle rampant poverty in the southeast and pardon PKK rebels to encourage them to lay down arms.

In northern Iraq, Turkish fighter jets and artillery pounded several locations near a key rebel base in Zap, near the Turkish border, and intensive clashes errupted on the ground, local Iraqi security sources said Wednesday.

Turkish forces were also dropping leaflets over the snow-bound mountains calling on the militants to surrender.

The army says it has so far killed at least 230 PKK militants and destroyed dozens of rebel hideouts, camps and ammunition depots, while losing 27 men.

The PKK claims to have killed around 100 soldiers, lost five and to have downed a Turkish attack helicopter.

burs-su/eb