Mr Koizumi, who earlier hurdled a no-confidence motion introduced in response to the bill, will begin work on Monday to schedule the dispatch of the self-defence force, Kyodo news agency said.
The force will represent the first deployment of Japanese troops since World War II to a country where there is ongoing fighting.
It paves the way for a reconnaissance mission expected to be dispatched by August, followed by a 1,000-strong contingent in October.
The Japanese forces’ mission would be to help resettle refugees, rebuild facilities and provide fresh water and supplies.
They are banned under the new legislation from providing weapons and ammunition for combat. —AFP