Prime Minister Junichiro Koizumi has told President Bush: "We must co-operate with each other and fight against terrorism dauntlessly."
Until recently, Japan's post-1945 constitution forbade its armed forces from playing anything other than a self-defence role.
However, the Japanese parliament has now passed a new anti-terrorism law, which allows Japanese soldiers to provide non-combat support for the US-led military operation against Afghanistan. Japan will also be allowed to offer medical facilities for US troops, participate in search-and-rescue operations and assist refugees. Changes to the law have provoked opposition both within Japan and from its neighbours, particularly China.