In a statement released late Wednesday, Taliban leader Mullah Mohammad Omar pressed members of the Afghan National Security Forces to carry out more so-called "insider" attacks against U.S. and coalition forces.
The message comes as U.S. forces confirmed on Thursday that two U.S. service members were killed by an individual wearing an Afghan National Police uniform.
The attack, which took place in Uruzgan province in southern Afghanistan, is still under investigation, according to a statement by U.S. Force-Afghanistan.
The Defense Department has yet to release the names of the dead, pending the completion of the investigation.
Including Thursday's casualties, more than 50 American and allied troops have been killed by Afghan forces in the past year.
Repeated insider attacks have created disarray within the Afghan ranks and chipped away at morale among U.S. and NATO forces, sowing seeds of distrust between coalition troops and local military and police units.
"It's one thing to be [killed in action] ... but to be shot in the back of the head at night by your friend" is something altogether different, International Security Assistance Force (ISAF) Deputy Chief of Staff of Operations Brig. Gen. Roger Noble of the Australian Army said in September.
The attacks will only become more effective as American units draw down and Afghan forces take increasing control of security operations in the country, Omar claimed.
"Increase your efforts to expand the area of infiltration in the ranks of the enemy and to bring about better order and array in the work. This tactic will achieve more fruitful results," according to the Taliban leader.
Earlier this month, a U.S. Army intelligence specialist and a CIA officer were killed in a suicide attack by a member of the Afghan intelligence corps.
Both Americans were among the six individuals killed during the strike on an Afghan intelligence outpost in the Maruf district of Kandahar province in southern Afghanistan.
Afghan and U.S. military officials were conducting a visit to the Afghan intelligence post when, during the visit, the intelligence officer detonated explosives he had concealed beneath his uniform, killing himself and the six others.
Despite increased counterintelligence efforts by Washington and Kabul to stem the tide of insider attacks in Afghanistan, the Pentagon's top military officer admitted no possible way to completely prevent the attacks from happening.
"We can dramatically lower the numbers [of attacks] ... but we can't prevent it," Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey said during an Oct. 10 speech at the National Press Club.