Koizumi reportedly told a dinner meeting at a Tokyo restaurant that he understands it will not be easy to decide what Japan should do for the U.S. if a war does indeed break out.

The participants were referring to the fact that Japan's war-renouncing Constitution substantially limits the extent of cooperation it could provide to Washington, despite being an ally.

Former Prime Minister Yasuhiro Nakasone urged Koizumi to tell U.S. President George W. Bush what Japan can and cannot do for Washington in the event of a war, according to a participant.

Kiichi Miyazawa, another former premier, told Koizumi to play the role of consultant for Washington to help prevent the U.S. from being isolated by the international community.

Among other former prime ministers at the meeting were Toshiki Kaifu, Ryutaro Hashimoto and Yoshiro Mori.