US-led investigators were on Tuesday given until December 23 to probe a NATO air strike killing Pakistani soldiers, threatening to prolong significantly Pakistan’s blockade on NATO supplies into Afghanistan. The US military appointed Brigadier General Stephen Clark, a one-star air force general based in Florida, to lead the investigation into the attack. The team, set to include a NATO representative, is yet to arrive in Afghanistan but an initial military assessment team went to the border at the weekend. The Afghan and Pakistani governments are also being invited to take part.