Japan and the United States on Sept. 26 inked a new logistics agreement to allow the Self-Defense Forces to supply fuel and ammunition to the U.S. military in the event of threats to Japan's national security.

The new Acquisition and Cross-Servicing Agreement (ACSA) is in line with the expanded role of the SDF brought about by the contentious national security legislation enacted last year.

Foreign Minister Fumio Kishida signed the agreement along with U.S. Ambassador Caroline Kennedy. Defense Minister Tomomi Inada was also in attendance at the signing ceremony held at the Foreign Ministry in Tokyo.

"This is an important agreement to allow for smoother cooperation that has been expanded due to the national security legislation," Kishida said.

Kennedy said the agreement was indispensable for effective cooperation between the U.S. military and the SDF.

The government plans to seek Diet approval of the new ACSA in the current extraordinary Diet session.

The opposition Democratic Party and Japanese Communist Party have criticized the government's failure to adequately explain the appropriate range of SDF rear logistic support to the U.S. military.

Public opposition to the national security legislation may have been why the Abe administration held off signing the new ACSA until after the July 10 Upper House election.

If the new ACSA is approved by the Diet, implementation could begin before the end of the year.

A high-ranking Foreign Ministry official said that the major area of logistic support being envisioned by the government is supplying fuel to the U.S. military.

The new agreement will allow the SDF to provide fuel to U.S. naval ships deployed to the Middle East to fight terrorism as well as U.S. aircraft ready to take off on combat missions.

The supplying of fuel in such circumstances would be permissible if the government determined there were situations threatening international peace and security or that may have an important impact on Japan's security.

In the past, special measures legislation had to be approved by the Diet before the SDF could provide fuel to the U.S. military, but under the new ACSA, no such Diet action will be needed.

The range in which the SDF can provide ammunition to the U.S. military will also expand greatly from the old ACSA. Under the former agreement, the SDF could provide ammunition only when Japan was under direct military attack or when such an attack was imminent.

However, the national security legislation passed in 2015 defined new situations under which the SDF could provide ammunition.

One would be a situation where an armed attack against a foreign country results in a clear threat to Japan's survival, or a so-called survival-threatening situation. Another would be a crisis in which Japan might face a possible attack if nothing was done. Such situations would allow Japan to provide logistic support to other militaries anywhere in the world.

The final scenario in which ammunition could be provided to the U.S. military would be a situation threatening international peace and security that the international community is collectively addressing under U.N. resolutions.

Japan could even provide ammunition to the U.S. Navy vessels on patrol in the open seas of the Sea of Japan as they prepare for a possible ballistic missile launch by North Korea.

Japanese officials feel, however, that it would be a rare case when the SDF is called upon by the U.S. military to provide ammunition.

(This article was written by Ryo Aibara and Kayoko Geji.)