Just hours before the high-level delegation flew in, Turkish President Abdullah Gul had warned that Ankara was "running out of patience," while Prime Minister Recep Tayyip Erdogan said US calls for restraint were misplaced.

"Our security forces are determined to move as soon as the situation arises," Erdogan told reporters during an official visit to Romania.

Last week, the Turkish parliament authorised the government to order a military incursion into northern Iraq against mountain bases used by the Kurdistan Workers' Party (PKK).

Since then, US and Iraqi calls for restraint have been met by Turkish demands that Washington and Baghdad make good on promises to crack down on PKK bases.

"We respect the territorial integrity and unity of Iraq, (but) we are running out of patience and we will not tolerate the use of Iraqi soil for terrorist activities," Gul said.

"We are fully determined to take all necessary steps to end this threat," he added.

The PKK has been fighting for self-rule in southeast Turkey since 1984, and Ankara says the rebels enjoy a safe haven in northern Iraq from which to launch cross-border raids on Turkish troops.

Erdogan insisted that while US Secretary of State Condoleeza Rice was welcome to voice hopes that Turkey would not overstep its border, "any decision on the necessity of such an incursion belongs to us."

The Turkish military said it had employed tanks and heavy artillery to thwart an attack Tuesday by "a large group" of PKK rebels against an army outpost on the border.

"More than 30 of the terrorists were rendered ineffective," said a statement on the website of the Turkish General Staff. Media reports said at least 30 rebels were killed.

It was the second confirmed attack in three days by the PKK against Turkish troops near the Iraqi border, after the ambush Sunday of a patrol that left 12 soldiers dead and eight taken prisoner.

The US deputy assistant secretary of state for European and Eurasian affairs, Matthew Bryza, said in Ankara that Washington was "doing what it can" to obtain the release of the captured soldiers.

"We've made a whole series of commitments on eliminating the PKK terrorist threat. We mean it. We'll deliver on those promises. We are working on it ... with the Turkish government and the Iraqi government," Bryza said.

"We know we need to produce concrete results," he added. "Hostage-taking is absolutely unacceptable."

With tensions running high, the Iraqi delegation, led by Defence Minister Abdel Qader Mohammed Jassim, arrived in Ankara in a fresh bid to avert any imminent Turkish strike.

The 11-member delegation includes Iraq's intelligence chief and senior officials from the Iraqi interior and foreign ministries, an Iraqi diplomat told AFP on the condition of anonymity.

The delegation also includes representatives of the two major Iraqi Kurdish parties in northern Iraq and a US major about whom no other details were available.

"We came with concrete steps, concrete proposals," said Jassim, Anatolia news agency reported.

Turkey's Foreign Minister Ali Babacan made the same call during a one-day visit to Baghdad on Tuesday.

"I told Baghdad that the delegation must come with concrete proposals, that the visit would be futile otherwise," Babacan said. "We need more than just words."

Earlier this week, Iraqi Prime Minister Nuri al-Maliki ordered the closure of all PKK offices in Iraq in what was seen as a concession to intense US and Turkish pressure.

However, the autonomous Kurdish regional government in northern Iraq on Thursday insisted there were no such offices to close.

"We have no idea about such an office," the regional government's spokesman, Jamal Abdallah, told AFP.

"If Prime Minister Maliki knows about such an office in Iraq, let him close it," he added.