Pakistan has blocked a key supply route for the US-led NATO force in Afghanistan after a cross-border helicopter attack mistakenly killed three Pakistani troops. The move comes one day after news emerged Pakistan had threatened to stop protecting NATO supply routes to Afghanistan after a series of attacks killed over seventy people. Around 100 NATO vehicles have already been held up today at Pakistan’s border with Afghanistan. Eighty percent of NATO’s non-lethal supplies in Afghanistan are delivered through Pakistan.