Pakistani officials gave NATO the go-ahead for the airstrikes that killed 24 of their own troops last weekend, the Wall Street Journal reported.
According to the article, US officials briefed on the preliminary investigation said Pakistan was unaware that their own forces were in the area.
According to Reuters, a Pakistani official denied the report.
The WSJ, however, quotes anonymous officials that claim that before calling in the airstrikes, US commandos contacted "a joint border-control center to determine whether Pakistani forces were in the area."
According to Reuters, US commandos thought they were being fired on by militants, but the millitants were actually Pakistani military personnel who had established a temporary campsite.
However, a Pakistani official denied the reports.
"Wrong information about the area of operation was provided to Pakistani officials a few minutes before the strike," said the official, who was not authorized to speak to the media.
A Pakistani official interviewed by GlobalPost also believed that the attack was not an accident.
He said that NATO uses real-time air photographs and satellite images of the border area instead of maps and that the outpost was about one-and-a-half years old, so NATO knew its coordinates.
“Striking this post by mistake is not possible,” he said.
The cross-border attack, which occurred last weekend, has caused public outrage in Pakistan, which has pulled out of next weekend's international conference on Afghanistan, Bonn II.
Pakistan's Army Chief Ashfaq Kayani has also stated that commanders in the Afghan border region can return fire if attacked, without waiting for permission, changing the rules of engagement.
"In case of any attack, you have complete liberty to respond forcefully using all available resources. You do not need any permission for this," Kayani said, according to Reuters.
According to the Guardian, Kayani is under immense pressure from within his own ranks. The NATO incident has piled further humiliation on the Pakistan military which is still recovering from the US special forces operation in May that killed Osama bin Laden deep inside Pakistan.