Pakistan's military said on Friday a communications breakdown prevented its air force from engaging NATO aircraft when they attacked two border outposts and killed 24 Pakistani soldiers.
The November 26 strike near the Afghan border has sparked fury in Pakistan and further complicated U.S.-led efforts to ease a crisis in relations with Islamabad and stabilise the region before foreign combat troops leave Afghanistan in 2014.
In a statement on its public relations website, Pakistan's military, which sets foreign and security policy, said that its response to the NATO strike could have been more effective had it been able to scramble its aircraft in time.
The response could have been more effective if PAF (Pakistan Air Force) had also joined in. However, it was no fault of PAF, the statement said.
The timely decision could not be taken due to breakdown of communication with the affected posts and, therefore, lack of clarity of situation, at various levels, including the Corps Headquarters and GHQ (General Headquarters).
Exactly what happened at the Pakistani posts along an unruly and poorly defined border is still unclear.
Pakistan said the attack was unprovoked, with officials calling it an act of blatant aggression.
U.S. officials, quoted in the Wall Street Journal on Friday, claimed Pakistani officials cleared the air strike without realising they had troops in the area.
The U.S. Embassy in Islamabad on Thursday released a video statement on YouTube by Ambassador Cameron Munter in which he expressed regret for the attack but stopped short of an apology.
Both the United States and NATO have promised to investigate the incident, expressing regret on the deaths of Pakistani soldiers but the White House said it was premature to consider apologising when an investigation was still in its early stages.
Pakistan has shown its anger over the attack by blocking supply routes for NATO forces in Afghanistan, and pulling out of an international conference in Germany next week on Afghanistan, depriving the talks of a central player in peace efforts.
Western leaders have urged Islamabad to rethink its decision to boycott the conference, but Pakistani Foreign Minister Hina Rabbani Khar said a reversal was unlikely.
I don't think there is a very strong case to reconsider this decision at all, she told reporters on Friday.
Pakistan has a long history of ties to militant groups in Afghanistan so it is considered to be uniquely positioned to help bring about a peace settlement, a top foreign policy and security goal for the Obama administration.
(Additional reporting by Augustine Anthony; Editing by Michael Georgy and Jonathan Thatcher)