A prominent U.S. newspaper is quoting U.S. officials as saying Pakistani authorities gave their approval for the November 27 NATO airstrike that killed 24 Pakistani troops, unaware that their forces were in the area.

The Wall Street Journal said Friday U.S. officials have offered the first “detailed explanation” of the “worst friendly-fire incident” of the 10-year-old war in Afghanistan

According to the unnamed U.S. officials, an Afghan-led assault force, including American commandos, was hunting Taliban militants when the group came under fire from an encampment along the Afghan-Pakistan border in the Mohmand tribal region.

The U.S. officials said the commandos thought they were being fired upon by militants but the assailants turned out to be Pakistani military personnel who had established a temporary campsite.

The report says the initial U.S. account from the field indicates the U.S. commandos contacted a joint border-control center, which said there were no Pakistani troops in the area, before requesting airstrikes against the encampment.

The Wall Street Journal says U.S. officials have acknowledged there were errors made on both sides of the incident, which has prompted Pakistan to boycott week's international conference on Afghanistan's future.

The newspaper says U.S. authorities have warned that the latest account is based on interviews with members of the commando team and could change as more information is gathered. It says a formal report is due to be completed by U.S. military investigators by December 23.