Whoever was to blame, the U.S. airstrikes that may have killed friendly fighters in Pakistan have inflamed the already touchy relations between Washington and Islamabad and could set back the struggle to stem violence along the Afghan border.
The bombings fueled anti-U.S. sentiment in Pakistan and raised questions about cooperative efforts to root out terrorism suspects in the lawless region, which American military leaders believe could spawn a new major attack against this country.
Little was certain about what happened.
U.S. diplomats offered apologies for the reported casualties, while the Pentagon insisted that surveillance drones tracking the bombings showed they hit exactly whom they intended: about a half dozen enemy fighters firing on coalition forces.
Defense Department press secretary Geoff Morrell said it was too early to know whether the strike killed 11 Pakistani paramilitary forces, as alleged by the angry Pakistani Army.
"Every indication we have is that this was a legitimate strike against forces that had attacked members of the coalition," he said.
Suspicions about U.S. operations
Whatever the case, it was certain the incident had fed suspicions about U.S. military operations inside Pakistan, as well as about Islamabad's inability to control Taliban or al-Qaida terrorists hiding in safe havens along the border.
The new Pakistani government has been trying to broker a peace deal with tribal leaders in the region. But U.S. officials have expressed skepticism about the plan, and there have been repeated questions about Pakistan's commitment and ability to wage a counterinsurgency battle.
The U.S. has promised to send 20-30 trainers to instruct Pakistani officers who will then train some 8,500 border Frontier Corps troops later this summer, said Adm. Mike Mullen, chairman of the Joint Chiefs of Staff. He also agreed that there is some merit in the negotiations that could peel off tribal leaders who would then become allies while isolating those who are extremists.
"I am learning as I go that these tribal areas are extraordinarily complex. There's no simple answer," said Mullen, adding that the U.S. wants peace agreements that can be enforced so that no insurgents cross the border.
Distracting from Pakistan's transition
Rick Barton, a Pakistan expert at the Center for Strategic and International Studies, said the incident had come at a bad time, when the new Pakistani government was already overwhelmed trying to find its way.
"The bad news with this kind of an incident is that it really distracts from the more important transition that's going on in Pakistan and it could really be exploited as an organizing tool to get people back to thinking the United States is the root cause" of problems in their country, Barton said.
"It could easily be used as a provocation for some of the groups that are most anti-American and are outside the government as well," he said.
The diplomatic strains were immediately apparent.
In Pakistan, U.S. Ambassador Anne Patterson was summoned to the Foreign Ministry, where Pakistan's government lodged a diplomatic protest.
"The United States regrets that actions ... on the night of June 10 resulted in the reported casualties among Pakistani forces who are our partners in the fight against terrorism," a U.S. Embassy statement said. It expressed condolences to the families of the dead.
And in Washington, State Department spokesman Gonzalo Gallegos said, "We are sad to see the reported loss of Pakistani life, however, our troops were defending themselves from a hostile act, which they have a right to do."
He said the incident "is a reminder that better cross-border communications between forces is vital."
U.S. still unsure who was killed
Military officials said the bombings are still being investigated and they don't know yet who exactly was killed. The Pentagon did not rule out the possibility that friendly forces were killed, but officials also did not discount the idea that paramilitary fighters may have attacked coalition troops.
The Pakistani army said the coalition airstrike hit a post of the paramilitary Frontier Corps and was a "completely unprovoked and cowardly act."
The U.S. military, meanwhile, said enemy fighters had begun firing on coalition troops about 200 meters inside Konar province. U.S. forces returned fire and also used unmanned drones to follow the insurgents.
As the drones watched, two F-15 fighters and a B-1 bomber launched about a dozen bombs on the enemy fighters who had crossed into Pakistan, U.S. military officials said.
In a statement, Combined Joint Task Force 101, based in Bagram, said coalition forces used the unmanned aircraft to maintain "positive identification of the enemy" firing at coalition troops. The statement also said that the operation was coordinated with the Pakistani forces.