Japan will agree on a draft convention to immediately and completely ban cluster bombs in principle, Chief Cabinet Secretary Nobutaka Machimura said Friday, marking a shift in Tokyo's position on the controversial munitions.

The draft treaty was adopted Friday in Dublin, where the Oslo process of talks to ban cluster bombs is taking place.

Prime Minister Yasuo Fukuda said he is glad that Japan decided to support the ban.

"It has been said for some time that cluster bombs are weapons that could cause humanitarian issues," Fukuda said. "(But) then, there is the issue of (national) security. I think the government considered both aspects thoroughly and came to this conclusion."

The Self Defense Forces have cluster bombs and say they are necessary for national defense.

Until now, Japan had been reluctant to agree to a comprehensive ban on cluster bombs. Tokyo had suggested a "partial ban," which prohibits the use of cluster bombs in urban areas, and mandates measures to abandon old model cluster bombs that often become duds after a transition period.

"It is not like (Japan) changed (its views) 180 degrees," Machimura said. "We considered the balance."

Machimura added that Japan will consider "various measures" to aim toward signing the treaty in December.

Machimura said there is a possibility Japan will dispose of its old-model cluster bombs and replace them with state-of-the-art cluster bombs that are excluded from the treaty.

The Oslo process began in February 2007, aiming to draw a treaty banning cluster bombs. But some countries that possess and use the bombs, including the U.S. and Russia, have not participated.