Staff Sgt. Robert Bales, the soldier charged with killing 16 Afghan civilians in what is considered the deadliest war crime by a single American soldier in the post-9/11 era, will plead guilty to avoid the death penalty, his lawyer said Wednesday.

In a brief interview as he rushed into a meeting with Sergeant Bales, John Henry Browne, the lawyer, said military prosecutors at Joint Base Lewis-McChord near Tacoma, Wash., had agreed to the plea, which could be made before a military judge next week.

A spokesman for the base, Lt. Col. Gary Dangerfield, said he could not confirm whether a deal had been struck or whether the two sides were in negotiations over a plea. But he said a plea hearing had been tentatively scheduled for next Wednesday.

“John Henry Browne is probably not saying it just to be saying it,” Colonel Dangerfield said. “But I can’t confirm whether they are in talks.”