(CNN) -- They are some of the world's ugliest weapons -- large, unreliable and notoriously inaccurate, wreaking havoc long after the end of armed conflict.
12-year-old Mohammed Haj Mussa lost his legs after a cluster bomb exploded in Lebanon.
Cluster bombs, which break apart in flight to scatter hundreds of smaller bomblets, are what the International Committee of the Red Cross (ICRC) calls a "persistent humanitarian problem."
On Monday, representatives of more than 100 countries plan to gather in Dublin, Ireland for a two-week conference to discuss a possible ban on the bombs.
"Cluster munitions are weapons that never stop killing," said ICRC president Jakob Kellenberger.
A cluster bomb's bomblets are meant to explode on impact, but many do not. Credible estimates show the weapons fail to explode between 10 and 40 percent of the time, the Red Cross said.
That means unexploded bomblets lie scattered across a target area, often exploding only when handled or disturbed -- posing a serious risk to civilians.
The most recent example is the 2006 war in Lebanon, where the U.N. estimates that Israel dropped about 4 million bomblets during the 34-day conflict. As many as 1 million may not have exploded, the Red Cross estimates.
The bombs have killed more than 250 civilians and disposal experts in southern Lebanon since the war. They were also used in the 1999 war in Kosovo.
"Very quickly after the Kosovo conflict, the major killer of civilians [was] not anti-personnel mines or anti-vehicle mines or conventional munitions, but these munitions," said Lt. Col. Jim Burke, a military advisor to the Irish Defense Forces. Watch report on ban proposal »
Bomblets from cluster munitions dropped during the 11-week conflict still litter fields, forests and vineyards. In more than 20 countries, the Red Cross says, 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.
Military forces consider cluster bombs important for use against multiple targets dispersed over a wide area, such as tanks or soldiers moving across the landscape. A single bomb can contain hundreds of sub munitions and cover an area of more than 29 square kilometers [18 square miles] .
"These can be delivered in the hundreds and hundreds of thousands in a few hours, in millions in a few days," said Peter Herby, head of the arms unit of the ICRC.
Still, some military leaders support the idea of banning the weapons.
"Military people are generally pretty practical," said Burke. "They don't want unreliable or inaccurate munitions. They also don't want to be in a position of being forced to use a weapon which is stigmatized internationally."
Though international humanitarian law prohibits indiscriminate attacks, there are no specific rules on cluster bombs.
States attending the Dublin conference plan to negotiate a new global treaty prohibiting the manufacture, sale, and use of the weapon, provide for their clearance from a battlefield and give assistance to their victims.
However, some of the world's top producers and users will be absent from the conference. They include the U.S., Israel, China, Russia, India and Pakistan, according to Human Rights Watch.
Other countries -- like the United Kingdom, Denmark, France and Japan -- want exceptions for certain cluster munitions within their arsenals, Human Rights Watch said.
"It is regrettable that the U.S. and a handful of other states continue to insist on their need to use a weapon that the rest of world is banning because it causes unacceptable harm to civilians," said Steve Goose, director of the arms division at Human Rights Watch. "But we believe that a strong new treaty will stigmatize cluster munitions to such a degree that it will be difficult for any country to use them without international condemnation."
The Red Cross wants the new treaty to prohibit inaccurate and unreliable cluster munitions -- those that cannot be targeted once released from their container and do not explode on impact.
The process to ban the weapon began in early 2007, when Norway invited governments to discuss new rules on cluster munitions with the aim of banning them by the end of 2008. The Dublin meeting is a major step in that process.
"We can act now to prevent human suffering on a potentially massive scale," Kellenberger said. "States must seize this important opportunity to prevent cluster munitions from killing and maiming countless other civilians."
-- CNN's Paula Hancocks contributed to this report.