"Until this morning, Afghanistan was not going to be a signatory," said Jawed Ludin, Afghanistan's ambassador to the Scandinavian countries and the leader of its delegation in Oslo, Norway, where the signing ceremony of more than 90 countries was taking place.
Ludin told The New York Times Karzai's shift was the result of pressure by human rights organizations and cluster-bomb victims.
Ludin's announcement was met by cheers in Oslo's City Hall, where the signing ceremony for the Convention on Cluster Munitions began Wednesday after two years of diplomatic work, the Times said. the treaty bars signatories from using, producing, selling or stockpiling cluster munitions.
Cluster munitions can be fired by artillery and rocket systems, or dropped by aircraft. They usually explode in the air, scattering dozens and possibly hundreds of bomblets over the target area.
"What we've adopted today is going to create profound change," said Jonas Gahr Stoere, Norway's foreign minister. "If you use or stockpile cluster weapons after today you will be breaking a new international norm."
Absent were the United States, Russia, China and Israel, the biggest producers and users of cluster munitions, human rights groups said.
Ludin said Afghanistan's reversal was possible because of an article in the treaty that permits signatory nations to engage in military operations with non-signatory nations.