( CNN ) -- More than 100 countries attending a conference in Dublin , Ireland formally adopted a treaty Friday to ban cluster bombs -- a large , unreliable and inaccurate weapon that often affects civilians long after the end of armed conflict . Cluster bombs are usually air-dropped shells that eject multiple small bomblets to kill enemy soldiers . A document released by Ireland 's Department of Foreign Affairs says the countries agreed never to use cluster munitions or the explosive bomblets they contain . The countries also agreed never to develop , acquire , retain or transfer cluster munitions . Countries attending the 11-day conference agreed to the treaty Wednesday but formally signed it Friday . The accord calls for a total , immediate ban of the weapons , strong standards to protect those injured by them , contaminated areas to be cleaned up as quickly as possible and for the weapons to be immediately destroyed , he said . Thomas Nash , coordinator of the CMC campaigning organization , said Wednesday : `` This is a great achievement for everyone who has been working hard to see the end of 40 years of suffering from these weapons . '' Though some of the biggest makers of cluster bombs , including the United States , Russia , China and Israel , were not involved in the talks and have not signed the accord , organizers predicted that those nations would nevertheless be pressured into compliance . `` Take the United States , '' Nash said . `` Almost all of its allies are here . They 've decided to ban these weapons . That 's going to make it extremely difficult , if not impossible , for the United States to ever use these weapons again , either on its own or in joint operations . '' The agreement requires the destruction of stockpiles of the weapons within eight years , he said . Cluster munitions , which break apart in flight to scatter hundreds of smaller bomblets , are what the International Committee of the Red Cross calls a `` persistent humanitarian problem . '' Most of a cluster bomb 's bomblets are meant to explode on impact , but many do not . Estimates show the weapons fail to explode on impact between 10 and 40 percent of the time , the Red Cross says . That means unexploded bomblets lie scattered across a target area , often exploding only when handled or disturbed -- posing a serious risk to civilians . Last week , Acting Assistant Secretary for Political-Military Affairs Stephen D. Mull called it `` an absolute moral obligation '' to rid a battlefield of unexploded ordnance after the battle . But he also predicted that the United States would not agree to any ban . `` We think that it is going to be impossible to ban cluster munitions ... because these are weapons that have a certain military utility and are of use , '' Mull said . `` The United States relies on them as an important part of our own defense strategy . '' Instead , he urged that the weapons be regulated `` to take humanitarian considerations into account '' and that `` technological fixes '' be pursued that would render them harmless after a battle . During the 34-day war in Lebanon in 2006 , the United Nations estimated that Israel dropped 4 million bomblets , 1 million of which may not have exploded , according to the International Committee of the Red Cross . More than 250 civilians and bomb-disposal operators have been killed or injured by them in southern Lebanon since the war ended . Cluster bombs were also used in the 1999 war in Kosovo . Lt. Col. Jim Burke , a military adviser to the Irish Defense Forces said they quickly became a major killer of civilians . In more than 20 countries , according to the ICRC , cluster bombs have created lasting `` no-go '' areas , rendering them as dangerous as minefields . Laos is the most affected country . Millions of bomblets dropped during the Vietnam War continue to kill civilians more than three decades later . Still , militaries consider cluster bombs important for use against multiple targets dispersed over a wide area , such as tanks or military personnel moving across the landscape . A single bomb containing hundreds of submunitions can cover more than 18 square miles . CNN 's Jacqueline Clyne contributed to this report .
111 countries formally agreeing treaty banning cluster bombs . U.S. not attending and not expected to agree to banning cluster bombs . Comment: