KABUL, Afghanistan — The U.S. apologized Wednesday for the deaths of two Pakistani paramilitary troops and the wounding of four others in a cross-border airstrike by U.S. helicopters that prompted Islamabad to close two vital supply routes used by the U.S.-led force in Afghanistan.
The latest flare-up comes as the Obama administration steps up public and private pressure on Pakistan to crack down on the Afghan Taliban and allied groups. The Wall Street Journal reported Wednesday that a new White House report to Congress says bluntly that Pakistan's civilian and military leaders have been unwilling to attack al Qaida and other terrorist groups.
Officials in Washington said that intensified strikes inside Pakistan by manned and pilotless aircraft — and reportedly also by U.S.-trained Afghan fighters — are an effort to pressure Pakistan to move against the Haqqani network, an insurgent group based in Pakistan's North Waziristan tribal area.
"The message is clear: If you won't act, we will," said one U.S. official in Washington, who requested anonymity because he wasn't authorized to talk to the news media about the issue.
Many U.S. officials think that elements within the Pakistani military are backing Islamist insurgent groups as part of a strategy to install a pro-Pakistan government in Kabul.
Wednesday's apology by the U.S. ambassador to Pakistan, Anne Patterson, came after the U.S.-led force in Afghanistan announced that a joint investigation into the Sept. 30 incident conducted with the Pakistani military found that the U.S. helicopters mistook the paramilitary troops for insurgents.
"We extend our deepest apology to Pakistan and the families of the Frontier Scouts who were killed and injured," Patterson said. "Pakistan's brave security forces are our allies in a war that threatens both Pakistan and the U.S."
In Kabul, U.S. Army Gen. David Petraeus, the commander of the U.S.-led International Security Assistance Force, or ISAF, also issued a statement, saying that the force "offers its deepest sympathy and condolences to the families of those killed and injured. We deeply regret this tragic loss of life."
There was no immediate official announcement from Islamabad about whether the two statements would be enough to persuade Pakistani authorities to reopen the supply routes from the port city of Karachi into landlocked Afghanistan.
A senior Pakistani official, however, said that he thought the border crossings at Torkham in the north and Chaman in the south would be reopened to vehicles hauling ISAF supplies.
Fifty percent of ISAF's supplies are carried on the routes. Twenty percent come down a road network from Central Asia, and the remainder is flown into Afghanistan, according to the U.S. Central Command.
Suspected Islamic militants torched dozens of trucks carrying ISAF supplies and killed at least one driver as they waited in Quetta, the capital of Baluchistan Province, for the Chaman border crossing to reopen, Pakistani authorities said. It was the seventh such attack on trucks carrying ISAF goods since the two border crossings were closed.
The senior Pakistani official, who requested anonymity because of the sensitivity of the issue, said that it's in Pakistan's interest to resolve the latest friction with the U.S.
"These things have to be calibrated carefully," he said. "We need to show how much they (the United States) depend on us, and then we can back away."
Pakistan denies that it has such a goal, and points out that it's lost hundreds of troops in offensives against the militants, even though most of its efforts have targeted domestic extremists, not those that are attacking ISAF and government forces in Afghanistan.
Pakistan's deeply unpopular civilian government faces considerable public anger over cross-border attacks on suspected insurgent targets by U.S. pilotless drone aircraft.
In a statement issued in Kabul, ISAF said that the investigation into the Sept. 30 incident found that the two U.S. helicopters had crossed into Pakistani airspace several times as they targeted insurgents just inside Afghanistan.
"Subsequently, the helicopters fired on a building later identified as a Pakistan border outpost, in response to shots fired from the post. The assessment team considered it most probable that they (the Pakistani paramilitary troops) had fired in an attempt to warn the helicopters of their presence," the ISAF statement said.
"We believe the Pakistani border guard was simply firing warning shots," said U.S. Air Force Brig. Gen. Tim Zadalis, the ISAF director of air plans, who led the investigation. "This tragic event could have been avoided with better coalition force coordination with the Pakistani military."
(McClatchy special correspondent Saeed Shah contributed from Islamabad.)
MORE FROM MCCLATCHY
Follow national security developments at McClatchy's Nukes & Spooks
Follow Afghanistan news at McClatchy's Checkpoint Kabul