It said the Self-Defence Force should have 20 personnel participating in the May 2-13 war games, alongside 3,614 from the United States, 2,655 from Thailand and 76 from Singapore.

"Japan's contribution is therefore small but its symbolic importance is considerable," said the authoritative military affairs magazine, which is published in London.

Jane's said the gesture was a sign of Tokyo's willingness to use the Self-Defence Force internationally, as outlined in a defence policy paper made public last December.

In its post-World War II constitution, Japan renounced the right to maintain armed forces for other than self-defence purposes, but that stance now is being debated as Tokyo sees North Korea and China as key security concerns.