Most of the stores will be held at embassies in Asia, where the H5N1 strain of the bird flu has killed at least 69 people since 2003, the nationwide Yomiuri newspaper reported.
Tamiflu is one of the few drugs believed to be effective in treating human victims of bird flu.
So far, most of the human cases in Asia have been traced to contact with sick birds, but experts fear a global flu pandemic that could kill millions if the H5N1 virus takes on human flu characteristics and passes easily between people.
The Foreign Ministry is currently negotiating with the Finance Ministry over a budget for the overseas stock, the Yomiuri said, without providing detailed figures, reported AP. P.T.