Hundreds of thousands of rusty munitions — leftovers from the Iran-Iraq war (search) — are scattered across the green fields and gentle hills of the two countries' common border.

Long ignored, they are now being harvested by insurgents who recycle them into crude but highly deadly bombs to use against U.S. and Iraqi troops.

Saddam-era ordnance, repackaged as roadside bombs or bundled together to use in car bomb attacks, has been the leading killer of U.S. soldiers in Iraq. Concerned about the growing trend, the military is paying Iraqis thousands of dollars for information about weapons caches.

"The munitions that are stockpiled in this area will for some time to come be a constant source of improvised explosive device material for someone that's willing to take the time to get them," Lt. Col. William M. Hart said.

Hart commands the 1st Squadron of the 278th Regiment from Athens, Tenn. His unit patrols about 60 miles of the Iraq-Iran border where much of the 1980-88 war was fought. It is impossible to know how many insurgent bombs originated from these weedy minefields. But the potential is enormous.

"We need to be working ... to limit munitions trafficking from the border westward into the population centers," Hart said. "If we do that, we will have been effective in at least taking away some of the insurgency's logistical support base."

The U.S. Army is reluctant to discuss reward amounts. Officials realize they are competing with insurgents and others buying old weapons, and they don't want to start a bidding war.

"We'd be naive to think we're the only ones paying them for munitions," said the 1st Squadron's Lt. Capt. Kevin Mick, a native of Columbia, Tenn., who frequently visits with villagers to check for new caches.

Since the regiment's arrival in November 2004, locals have turned in over 7,000 munitions.

Critics say the program provides incentives for poor, untrained Iraqis to do dangerous work. Advocates say Iraqis are helping to demilitarize their country and disable weapons that could be used to kill or maim civilians and soldiers.

The military has allocated hundreds of millions of dollars to the Army Corps of Engineers (search) and private contractors to destroy munitions throughout the country. But there are still more than enough to guarantee insurgents a steady supply for the foreseeable future.

Estimates of the number of mines before the 2003 U.S. invasion range between 8 million and 12 million. In the western half of Diyala province (search), next to the border area, more than 1,400 improvised bombs have been located since November 2003, according to U.S. military statistics.

The weapons remain a threat to life along the border, where roads are lined by piles of stones or sticks stuck in the ground — primitive warnings of nearby danger. Anti-personnel mines can be seen jutting from the sand, and mortars and rocket-propelled grenades that skipped across the desert a quarter century ago lie buried in soft beds of sand, still dangerously sensitive.

Iraqi soldiers said earlier this month they found the bodies of two shepherds amid a herd of aimless sheep, the apparent victims of leftover munitions.

U.S. soldiers patrolling near the border recently picked up 21 pieces of rusty munitions from a villager who flagged down the same group a few hours later to say he had also collected some 200 anti-tank mines. A shepherd on the same road two days earlier stopped a convoy of Humvees to point out a protruding land mine just off the road.