The health ministry's target of stockpiling enough Tamiflu, the antiviral drug considered the first line of defense against the H5N1 avian flu virus, to cover 21 million people can be met in two years at the earliest, sources said Saturday.

The ministry believes it can procure the drug for 10 million people each in fiscal 2006 and 2007, the sources said. It is to be stored by the central and prefectural governments.

Tamiflu is produced by Swiss drug giant Roche AG and imported for sale in Japan by Chugai Pharmaceutical Co., a Tokyo-based member of the Roche group.

Chugai Pharmaceutical has said it has enough on hand now to treat 12 million ordinary flu patients, they said.

For a new strain, it can import the drug for 10 million people in fiscal 2006 and, if the orders are placed by December, for another 10 million people in fiscal 2007, the sources said.

The ministry has decided to negotiate with Chugai Pharmaceutical on Tamiflu procurement on behalf of both the central and prefectural governments, they said. It plans to begin procurement procedures next month.

As fears mount about a possible human flu pandemic deriving from avian influenza, the ministry boosted its Tamiflu stockpile target on Oct. 14 from covering 15 million people to 25 million people, including drugs stockpiled by the private sector.

The target is based on the assumption that one-quarter of Japan's population of 127 million could contract the new influenza strain.

The central and prefectural governments would each stockpile Tamiflu for 10.5 million people, while the private sector would keep enough doses for 4 million people.

The ministry believes the private sector's portion will be obtained from surplus Tamiflu left over in the spring, the sources said.