Peace talks to determine Afghanistan’s future have been hindered by a recent airstrike by the North Atlantic Treaty Organization on Pakistani soldiers.

On Nov. 24, NATO performed an airstrike, which killed 24 Pakistani soldiers at border posts they were running, according to BBC News. NATO claims the airstrike was a “tragic unintended accident,” though Pakistani officials claim their troops were asleep and that the area had been free of any suspicious activity.

Reuters called this “the worst friendly-fire incident of the 10-year-old war,” and reported that U.S. officials claimed the airstrike was cleared with a border control center run by U.S., Afghan and Pakistani forces.

Pakistani officials, however, have said the airstrike was in progress before they received any such communication.

According to Reuters, the U.S. has declared that they will run their own investigation of the incident. A formal report is expected by Dec. 23.

This airstrike is a severe blow to Pakistan’s relationship with the U.S. at a crucial time. The U.S. hoped to have Pakistan involved in the Bonn conference, meant to decide Afghanistan’s future.

Pakistan shares a border with Afghanistan and has assisted the U.S. throughout the war. According to the Washington Post, officials want Pakistan’s cooperation because of their perceived influence with the Taliban.

The Pakistani Taliban is active but disorganized, according to MSNBC. However, they did train the Pakistani-American Times Square car bomber.

Al Jazeera reported Mark Toner, U.S. state department spokesman, said, “We hope that they do, in fact, attend this conference because this is a conference that is about Afghanistan and building a more stable and prosperous and peaceful Afghanistan. And so that is very much in the interests of Pakistan.”

Following the attack, Pakistan has decided not to attend the conference, reported Al Jazeera.

According to Robert Duncan, visiting assistant professor of political science, Pakistan could be backing out of the talks for other reasons. He claims that Pakistan wants to keep Afghanistan in chaos to distract from the internal problems of the Pakistani government.

“Peace in Afghanistan does not advance the Pakistani agenda,” said Duncan.