By Imogen Foulkes
BBC News, Geneva
A new international law is coming into force requiring countries to clear up unexploded bombs and mines or pay teams of de-miners to do it.
The use of cluster bombs in Lebanon focused world attention
The treaty on explosive remnants of war covers ordnance such as land mines and cluster bombs.
At the same time, in Geneva, a UN arms review conference is under way amid growing pressure on member states to discuss a ban on cluster bombs.
Aid agencies say such bombs should be banned, not just cleaned up.
'Cold War remnant'
There are thought to be billions of cluster bombs stockpiled around the world.
One billion of them are in the United States alone.
However, the US is one of the key nations, along with China and Russia who are not keen to discuss the issue.
Cluster bombs have been around for decades, used in wars from Vietnam to Kosovo.
Many military leaders believe they are useful in certain circumstances.
Ronald Bettauer, head of the US delegation to the weapons review conference in Geneva, says the time is not right to start discussing a ban.
"Our military and the military of many other countries believe they need these munitions... They actually feel the cluster munitions in some situations will be more humane than blanketing the area with high explosives."
However, the conflict in Lebanon has focused world attention on this weapon.
De-miners say up to one million unexploded cluster bombs in Lebanon will pose a threat to civilians for years.
Now the International Committee of the Red Cross has proposed a treaty to ban unreliable cluster bombs and to forbid their use at all in populated areas.
UN Secretary General Kofi Annan has also called for action.
Simon Conway, of Landmine Action, says cluster bombs are a remnant of the Cold War.
"The wars that we fight now are wars amongst the people where we're fighting for the will of people, and you can't achieve your military or strategic aims if you kill large numbers of civilians in the process."
At the start of the weapons review conference, only half a dozen countries backed negotiations on cluster bombs.
After just a few days, that number has tripled, with more joining all the time.
Non-governmental organisations had not expected such support.
When the conference ends later this week, it is thought member states will agree to start discussing ways to control the weapon.