ISLAMABAD,Pakistan- Pakistan, enraged by a NATO cross-border air attack that killed 24 soldiers, could withdraw its support for the US-led war on militancy if its sovereignty is violated again, the foreign minister suggested in comments published on Thursday.

The South Asian nation has already shown its anger over the weekend strike by pulling out of an international conference in Germany next week on Afghanistan. It stood by that decision on Wednesday, depriving the talks of a central player in efforts to bring peace to its neighbour.

"Enough is enough. The government will not tolerate any incident of spilling even a single drop of any civilian or soldier's blood," The News newspaper quoted Foreign Minister Hina Rabbani Khar as telling a Senate committee on foreign affairs.

"Pakistan's role in the war on terror must not be overlooked," Khar said, suggesting Pakistan could end its support for the US war on militancy. Despite opposition at home, Islamabad backed Washington after the September 11, 2001, attacks on the United States.

Pakistan military sources also said it had cancelled a visit by a 15-member delegation, led by the Director General of the Joint Staff, Lieutenant-General Mohammad Asif, to the United States that was to have taken place this week.

NATO helicopters and fighter jets attacked two military border posts in northwest Pakistan on Saturday in the worst incident of its kind since 2001.  

Details are still sketchy about what happened in the early morning hours, but Pakistani military sources said the attack came in two waves.

"The attack began at around 12:05 am and lasted for about 30 minutes, when the contacts were made and it was discontinued," said one source.

The source said NATO helicopter gunships and jet fighters came back after 35 minutes. The Pakistanis returned fire in a battle that lasted for another 45 minutes.

When it was over, 24 Pakistani soldiers were dead and 13 wounded.

The two posts in question -- Volcano and Boulder -- are perched about 8,000 feet high on a ridgeline near the Afghan border. They are among about 28 such posts in Mohmand Agency set up to prevent cross-border movements by Taliban miltants, another military source said.

The source said that there were no militants in the area, however, because they had been flushed out by a Pakistani military operation conducted over the year.

The top US military officer denied allegations by a senior Pakistani army official that the NATO attack was a deliberate act of aggression.

General Martin Dempsey, chairman of the U.S. military's Joint Chiefs of Staff, told Reuters in an interview: "The one thing I will say publicly and categorically is that this was not a deliberate attack."  

The army, which has ruled Pakistan for more than half of its history and sets security and foreign policy, faced strong criticism from both the Pakistani public and the United States after Osama bin Laden was killed in a secret raid by US special forces in May.  

The al Qaeda leader had apparently been living in a Pakistani garrison town for years.  

Pakistanis criticised the military for failing to protect their sovereignty and US officials wondered whether some members of military intelligence had sheltered him. Pakistan's government and military said they had no idea bin Laden was in the country.  

The army seems to have regained its confidence and won the support of the public and the government in a country where anti-American sentiment often runs high.

Protests have taken place in several cities every day since the NATO strike along the poorly-defined border, where militants often plan and stage attacks.

In an apparently unrelated attack, a bomb blew out a wall of a government official's office in Peshawar, the last big city on the route to Afghanistan, early on Thursday, police said. There were no reports of casualties.  

The United States has long wanted Pakistan, whose military and economy depend heavily on billions of dollars in American aid, to crack down on militant groups that cross its unruly border to attack Western forces in Afghanistan.

More recently, US Secretary of State Hillary Clinton asked Pakistan to bring all militant groups to the negotiating table in order to stabilise Afghanistan.

The NATO attack makes Pakistani cooperation less likely.

NATO hopes an investigation it promised will defuse the crisis and that confidence-building measures can repair ties.  

But the army is firmly focused on the NATO attack, and analysts say it is likely to take advantage of the widespread anger to press its interests in any future peace talks on Afghanistan.

Pakistan says it has paid the highest price of any country engaged in the war on militancy. Thousands of soldiers and police have been killed.

Critics allege Pakistan has created a deadly regional mess by supporting militants like the al Qaeda-linked Haqqani network to act as proxies in Afghanistan and other groups to fight Indian forces in the disputed Kashmir region.

"The sacrifices rendered by Pakistan in the war on terror are more than any other country," Khar was quoted as saying. "But that does not mean we will compromise on our sovereignty."