US Army snipers in Iraq are ordered to "bait" areas with explosives and ammunition and then kill whoever picks them up, according to court documents.
A US Army officer said only enemy combatants would pick up the 'bait'
The classified programme is described in statements disclosed by lawyers for three US soldiers accused of planting evidence on Iraqis they had killed.
It is unclear how widely the tactic may have been used in Iraq or how many people may have died as a result of it.
The US army has declined to confirm whether the "baiting" policy exists.
"To prevent the enemy from learning about our tactics, techniques and training procedures, we don't discuss specific methods targeting enemy combatants," a spokesman, Paul Boyce, said on Monday.
Mr Boyce did say, however, that no programme authorised the use of "drop weapons" to make a killing appear legally justified, as the three snipers are accused of doing.
In a sworn statement published by the Washington Post, the leader of an elite US Army Ranger sniper scout platoon, Capt Matthew Didier, described baiting as "putting an object out there that we know they will use, with the intention of destroying the enemy".
"Basically, we would put an item out there and watch it," he said.
"If someone found the item, picked it up and attempted to leave with the item, we would engage the individual as I saw this as a sign they would use the item against US Forces."
Capt Didier said members of the US military's Asymmetric Warfare Group had visited his unit in January and given them "drop items" to be used "to disrupt the AIF [Anti-Iraq Forces] attempts at harming Coalition Forces and give us the upper hand in a fight", according to the Post.
The Asymmetric Warfare Group grew out of a taskforce created after the US-led invasion of Iraq in 2003 to develop methods to combat roadside bombs.
Within months of the "baiting" programme being introduced, three snipers from Capt Didier's platoon, which was attached 1st Battalion of the 501st Infantry Regiment, were charged with premeditated murder after using "drop items" to make shootings appear legitimate, according to the Post.
Human rights groups say innocent civilians could have been killed
The court martial of one of the accused soldiers, Specialist Jorge Sandoval Jr, is due to begin in Baghdad on Wednesday.
He and Staff Sgt Michael Hensley are accused of leaving a spool of wire in a pocket of a man who Spec Sandoval shot in April. A third soldier, Sgt Evan Vela, is facing similar charges.
Gary Myers, a lawyer for Sgt Vela, said his client had acted "pursuant to orders".
"We believe that our client has done nothing more than he was instructed to do by superiors," Mr Myers told the Associated Press.
James Ross, the legal and policy director of Human Rights Watch, said the dispersal of ammunition and explosives by US forces as a method of targeting insurgents would present obvious human rights problems.
"It seems to me that there are all sorts of reasons that civilians would want to pick up ammunition that is sitting on the ground," he said.