BY : Guardian News

Pakistani troops fired on US forces entering the country's lawless tribal region yesterday, marking a further deterioration in ties between the two allies in the "war on terror". Details of the incident in south Waziristan were unclear but, according to local security officials and tribesmen, two American helicopters breached Pakistani airspace in the early hours, but retreated when they came under fire.

The US forces were likely to have been on a hit-and-withdraw mission against suspected militants in the area, similar to the first documented American ground raid into the tribal territory this month when helicopters flew in commandos. That enraged Pakistan's army and public.

A security official in south Waziristan said yesterday: "American helicopters came and there was a space [border] violation. Pakistani scouts [paramilitary troops] fired artillery as a warning and they left. The helicopters did not land."

Other reports said troops had fired at the helicopters, which were just inside Pakistani territory. One official said the fire came from Pakistani soldiers based at a frontier checkpost known as BP-27.

The Pakistani army admitted that a skirmish took place, but denied that its troops were involved. "The villagers had some firing incident," said a spokesman, Major General Athar Abbas. "But who fired at who, I cannot confirm." The US military denied there had been any operation.

"We did not have any forces or helicopters on or near the border," said Mark Swart, a spokesman for the American military at Bagram airbase in Afghanistan.

The US raid earlier this month, which killed up to 20 people including civilians, was finally admitted by the Pentagon, but not on the record.

The US believes that the tribal area is used as a safe haven by Taliban and al-Qaida militants who are fighting American and coalition forces in Afghanistan. Last week, Admiral Mike Mullen, chairman of the joint chiefs of staff, said a new strategy for Afghanistan was needed that incorporated the tribal territory. President George Bush is believed to have signed a secret order allowing US forces to operate in the tribal area, even though the UN mandate for international forces in Afghanistan does not extend into Pakistan.

Bush is thought to be in a desperate push for a trophy strike against al-Qaida's top leadership, which is likely to be based in the tribal area, before he leaves office.

Analysts believe the new policy risks a clash between the Pakistani and US militaries and threatens to undermine the new democratic government in Islamabad. As well as the ground assault, there has been a big increase in the number of US missiles fired from unmanned aircraft at militant targets in the tribal area. These, too, have claimed dozens of civilian lives.

"This kind of situation cannot go on, because any government in Pakistan will get destabilised," said Hasan Askari Rizvi, a security analyst in Lahore. "The Americans don't realise that if there is instability in Pakistan, their war on terror cannot be pursued. If everybody turns against America, no [Pakistani] government will be in a position to support the war on terror."