The Situation Room

STARR (voice-over): U.S. and Afghan forces in the remote mountains of Eastern Afghanistan. Six U.S. troops lost their lives here trying to dislodge the Taliban and protect local citizens But it's the threat of insurgents wearing Afghan uniforms and attacking one secure areas that is increasingly worrisome. Former Afghan war commander, Retired Lt. Gen. David Barno says the Taliban are getting ready for U.S. withdrawal.

LT. GEN. DAVID BARNO, U.S. ARMY (ret.): The approach is not only to try and find ways to get inside the wire as it were to kill Americans but also to suddenly undermine psychologically American confidence in their Afghan counterparts.

STARR: On Monday, a man wearing an Afghan army uniform entered the security compound of the defense ministry and opened fire, killing two. Five U.S. soldiers were killed Saturday when a suicide bomber wearing an Afghan military uniform struck a military base. On Friday, the Kandahar police chief was killed by a suicide bomber wearing a military uniform,. U.S. military officials say civilians still suffer most from the suicide attacks.

In February and March of 2010, insurgents killed or injured 82 Afghan civilians. This year, it was 353, a 330 percent jumped. But Barno warns U.S. troops shouldn't feel too secure.

BARNO: We felt in the past that we are inside of our bases and if we are working with our Afghan counterparts that we were relatively secure. And I think this whole strategy now puts that into question.