The Pentagon will allow the United States military to once again arm itself with older cluster munitions, a type of weapon that has been banned by 102 countries largely because of concerns that they disproportionately harm civilians.
The change, detailed in a memo to be released Friday, reverses a prohibition issued under President George W. Bush, and appears to be a concession by the United States that finding safer variants of the weapons has so far failed.
Most American cluster munitions held abroad appear to be positioned for a possible war with North Korea. Under a 2008 agreement, the Pentagon maintains a stockpile of more than 1.5 million cluster munitions, containing over 90 million bomblets, in South Korea.
Cluster munitions include a wide variety of rockets, bombs, missiles and artillery projectiles that scatter smaller weapons, called submunitions, over a target area. Some dispensers can release as many as several hundred bomblets.
Though the United States is not a signatory to the international treaty banning the weapons, it pledged in June 2008 to sharply restrict their use and reduce risks to civilians.
Arguments against the use of cluster munitions are twofold. Because of their wide dispersal pattern, submunitions may strike civilians who are not even close to intended targets. Additionally, many types of submunitions fail to properly detonate at a higher rate than other weapons, resulting in bomblet “duds” that can explode even years later and kill civilians.
Military bomb disposal technicians have estimated that cluster munitions have a dud rate as high as about 20 percent. The 2008 policy, signed by the defense secretary at the time, Robert M. Gates, gave the Pentagon 10 years to develop and use cluster munitions that “do not result in more than 1 percent unexploded ordnance” by 2018. Mr. Gates declined to comment on Thursday.
At the time he signed the memo, the American military had only one weapon it claimed met that goal, the BLU-108 Sensor Fuzed Weapon, which the Air Force used widely during the 2003 invasion of Iraq.
But that 1 percent claim was quietly walked back in 2016 after photographs in Yemen showed large numbers of dud Sensor Fuzed Weapons that were dropped by Saudi Arabian warplanes. The United States provided those cluster bombs to the Saudis.
Shortly afterward, the bomb’s manufacturer, Textron Systems, announced that it would cease production of Sensor Fuzed Weapons. Textron’s former chief executive officer, Ellen M. Lord, now serves as the under secretary of defense for acquisition, technology and logistics. However, Textron has no plans to restart manufacturing cluster munitions, said a spokesman for the company, David Silvestre.
The last known use of cluster munitions by the United States military was a December 2009 strike in Yemen, when Navy warships fired multiple Tomahawk cruise missiles carrying bomblets. The target was “a confirmed A.Q.A.P. terrorist training camp,” according to a former senior American military officer familiar with the decision to launch that attack, using a term for Al Qaeda in the Arabian Peninsula. The military believed there were no civilians in the area, said the former officer, who spoke on the condition of anonymity to discuss details of the sensitive operation.
The American military’s account has been publicly challenged. Amnesty International reported that the 2009 attack killed 41 people, including 14 women and 21 children. The group also reported finding dud submunitions at the site.
It is unclear whether the new change will cease the destruction of the existing cluster munition stockpile, as required by the 2008 policy. Older cluster artillery shells, for example, containing submunitions with a high dud rate, for years have been sent to an Army ammunition plant in McAlester, Okla., to be demilitarized.
A spokesman at the plant said he was unaware of the policy change and did not know whether demilitarization operations were still active there.
Thomas C. Crosson, a Pentagon spokesman, said that the new policy maintained the goal of procuring only cluster weapons with a dud rate of 1 percent or less, but that the deputy defense secretary could waive those limits “under extreme wartime circumstances.”
Army data from earlier this year, obtained by The New York Times, said that the American arsenal contained more than 2.2 million cluster munitions in the United States and 1.5 million abroad — most of them in South Korea.