Islamabad - Admiral Mike Mullen, chairman of the US Joint Chiefs of Staff, on Wednesday tried to lessen military tensions with Pakistan as he met the country's senior military and civilian leadership.

During his visit, Pakistani helicopter gunships and artillery pounded Taliban militant positions in the country's lawless tribal areas along the Afghan border, killing at least 19 rebels, the army said.

The US pursuit of al-Qaeda and Taliban militants inside Pakistan's tribal belt has strained relations between the two allies and the officials of the two countries have been engaged in a war of words in recent weeks.

Mullen met Pakistan's military chief, General Ashfaq Parvez Kayani, in the garrison town of Rawalipindi outside Islamabad and later held a meeting with Prime Minister Yousaf Raza Gilani in the capital.

The leaders reviewed the progress of Pakistan's efforts to combat militancy, violence and terrorism in talks that were described by the United States as being "extremely frank, positive and constructive."

Mullen "reiterated the US commitment to respect Pakistan's sovereignty and to develop further US-Pakistani cooperation and coordination on these critical issues that challenge the security and well-being of the people of both countries," according to a statement released by the US embassy.

Earlier, an official privy to the Kayani-Mullen talks said Pakistan's army chief "expressed his concerns on US attacks inside Pakistan and emphasized that the foreign troops could not be allowed to conduct operations on Pakistani soil."

Mullen was on a previously unannounced visit as US military operations inside Pakistan, including the first known ground raid that killed 20 people on September 3, have fuelled anger in the country with increasing calls to abandon cooperating with Washington's war on terrorism.

A week after the assault, Kayani, in a strongly worded statement, said the country's sovereignty would be defended "at all costs." He added that "such reckless actions only help the militants and further fuel militancy in the area."

Pakistan's north-western tribal regions are considered safe havens for al-Qaeda and Taliban leaders who have regrouped and established facilities to train fighters for attacking coalition forces in Afghanistan.

Mullen last week said the United States was not winning its war in Afghanistan and, therefore, needed a "new, more comprehensive strategy," sparking speculation that it would increase its focus on independent operations inside Pakistani territory to eliminate key targets.

A New York Times report that US President George W Bush had secretly approved ground attacks without the consent of Pakistan gave credence to the speculation of changing US tactics.

However, the Pakistani military insisted that it reserves the right to defend the territorial integrity of the country. Security officials said Monday that government troops and tribesmen prevented a US incursion into the South Waziristan tribal district's Angor Adda village, the scene of an earlier ground assault.

On Wednesday, at least 19 militants were killed by the Pakistani military, an army spokesman said.

"In the Bajaur tribal district today, the ground troops secured several areas and moved forward toward Loi Sam, the militants' headquarters," Major Murad Khan said Wednesday.

He said the positions insurgents had "fortified around Loi Sam were engaged by artillery and gunship helicopters, leaving at least 19 militants killed and numerous injured."

Clashes in Bajaur erupted in early August when dozens of rebels attacked a checkpoint on a strategic hilltop along a route previously used by militants to cross into Afghanistan and attack international forces there.

Around 800 militants have been killed in the clashes, according to official data. But it does not include civilian casualties, which remain unaccounted for because of the difficult geographical and security situation of the area.

Tens of thousands of people have been displaced because of the fighting in the district, which remains inaccessible to mainstream media. (dpa)