Pakistani and U. S. officials have formally signed an agreement before they______.

Pakistani and U. S. officials have formally signed an agreement allowing NATO supply trucks to travel through Pakistan into Afghanistan through the end of 2015.(21)The deal comes a day before the head of Pakistan’s spy agency begins talks in Washington with his American counterpart on anti-terrorism cooperation.
    For more than a decade, U. S. -led coalition troops fighting the Taliban in Afghanistan have received supplies through Pakistan without a formal agreement between Islamabad and Washington.(22)But a coalition airstrike in November that mistakenly killed 24 soldiers prompted Pakistani authorities to shut down the NATO supply lines and reevaluate future engagement with the United States. After months of negations with Washington and a U. S. apology for the deaths of the soldiers, Islamabad reopened two border crossings to coalition cargo earlier this month.