ISLAMABAD, Pakistan - The deaths of 11 Pakistani paramilitary soldiers from U.S. air and artillery strikes during a clash with insurgents on the Afghan border is likely to complicate the already strained relations between the two countries.
The incident Tuesday night underscored the often faulty communications involving American, Pakistani and Afghan forces along the border, and the ability of Taliban fighters and other insurgents to use havens in Pakistan to launch attacks into neighboring Afghanistan.
The attack comes at a time of rising tension between the United States and the new government in Pakistan, which has granted wide latitude to militants in its border areas under a new series of peace deals, drawing criticism from the United States. NATO and U.S. commanders say cross-border attacks in Afghanistan by insurgents have risen sharply since talks for those peace deals began in March.
Although Pakistani government officials softened their response through the day, the Pakistani military released an early statement calling the airstrikes "unprovoked and cowardly." Shaken by the initial Pakistani reaction, Bush administration officials braced for at least a short-term rough patch in relations with Islamabad.
"It won't be good," said a Pentagon official who followed developments closely through the day. The official spoke on condition of anonymity.
The precise circumstances surrounding the reported deaths remained unclear, and U.S. officials said an American-Pakistani investigation was expected to begin immediately.
According to accounts from U.S. officials, the incident started when Taliban fighters from Pakistan crossed about 200 yards into Kunar province, on the Afghan side of the border, and attacked U.S.-led forces with small arms and rocket-propelled grenades.
After coalition forces returned fire, driving the insurgents back into Pakistan, two U.S. F-15E fighter-bombers and one B-1 bomber dropped about a dozen bombs on the attackers. An Air Force statement said the militants were struck "in the open and in buildings in the vicinity of Asadabad."
A spokesman for the Taliban said their forces had attacked a U.S. and Afghan position near the border and that eight of their fighters had been killed and nine wounded in the fighting.
Before the airstrike, a Pentagon official said, U.S. forces alerted a Pakistani military liaison officer, trying to ensure that friendly troops were out of harm's way. But the Pakistani officer was either unaware that Pakistani forces had moved into the area near the insurgents or the Pakistani forces never got the word, American officials said.
"They got caught in the wrong place at the wrong time," the Pentagon official said.
Prime Minister Yousaf Raza Gillani of Pakistan denounced the attack in Parliament and said he had instructed the Foreign Ministry to make a formal protest to the U.S. ambassador, Anne Patterson.
But the Pentagon press secretary, Geoff Morrell, told reporters in Washington that "every indication we have at this stage is that it was a legitimate strike in self-defense." U.S. rules of engagement bar American forces from crossing or firing into Pakistan except to protect themselves.
By Tuesday afternoon, Pakistan's new ambassador to Washington, Husain Haqqani, had softened his government's reaction, telling Reuters: "We do look upon it as not an act that should cause us to reconsider our partnership but rather to find ways of improving that partnership."
Seth Jones, an analyst with the Rand Corp. who was conducting research in Kunar province last week, said: "It's almost surprising more of this hasn't happened, given the vast amount of traffic across the border. This creates a real serious impetus for the U.S. to coordinate more closely with Pakistan forces."
U.S. officials in Pakistan and in Washington, while expressing regret at the Pakistani deaths, said the incident underscored the need to improve coordination with Pakistani security forces operating near the border, including the Frontier Corps, a paramilitary force of about 85,000 members recruited from ethnic groups on the border.
U.S. and Pakistani officials say the Frontier Corps, which is drawn from Pashtun tribesmen who know the language and culture of the tribal areas, is the most suitable force to combat an insurgency over the long term in the border region, where the regular Pakistani military often is not welcomed.
Gonzalo Gallegos, a State Department spokesman, said, "This is a reminder that better cross-border communications between forces is vital."