As the attorney for an Army soldier accused of killing 16 Afghan civilians prepared to meet his client for the first time Monday, a retired U.S. general suggested the fallout from the massacre could see American troops begin to return home from Afghanistan within weeks.

Staff Sgt. Robert Bales stands accused of a shooting rampage in southern Afghanistan's Kandahar province, allegations that have significantly heightened already tense U.S.-Afghan relations and intensified a debate about whether to pull American troops ahead of 2014 planned withdrawal.

Following the March 11 shootings in two neighboring villages just outside a U.S. outpost in the Panjwai district, Afghan President Hamid Karzai demanded troops withdraw from villages and return to their bases. He said relations between the two countries were "at the end of their rope."

If U.S. troops are not allowed to return to the villages and resume their mission, "the United States mission is changed," retired Maj. Gen. James A. "Spider" Marks, a former commander of the U.S. Army Intelligence Center, told CNN's Don Lemon on Sunday.