KABUL: A US-led investigation into a Nato air strike that killed 24 Pakistani troops near the Afghan border will report its initial findings by December 23, officials said Tuesday.

The chief of US Central Command, which oversees US forces in Afghanistan and the Middle East, appointed Brigadier General Stephen Clark, a one-star air force general, to lead the investigation, the US military announced.

The probe is expected to provide an initial report by December 23, it added.

Pakistan has reacted to Saturday's air strike with fury, cutting off crucial supply routes to Nato forces in Afghanistan, and ordering US personnel to vacate an air base reportedly used by CIA drones and a review of US relations.

Clark will lead the investigation with input from Nato and its International Security Assistance Force.

The Afghan and Pakistani governments are also being invited to take part, despite Pakistan's furious response to the attack.

“It is USCENTCOM's intent to include these government representatives to the maximum extent possible to determine what happened and preclude it from happening again,” the US military said.

“The investigation team will focus their efforts on the facts of the incident and any matters that facilitate a better understanding of the circumstances surrounding the deaths and injuries of the Pakistani forces.” ISAF sent an initial assessment team to the border over the weekend.

A Western military official in Kabul, speaking on condition of anonymity, said the probe team had yet to arrive in Afghanistan but insisted its findings would be reported “way quicker” than initially expected.

The source said it was not unusual for US Central Command to carry out this kind of investigation rather than ISAF, which usually undertakes probes into incidents such as civilian casualties.

ISAF refused to comment when asked whether US Special Forces had been operating in the area when the air strikes were called in.