WASHINGTON — 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 released on 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.