TOKYO – Japan and the United States have been discussing a scenario, in which the U.S. military would use nuclear weapons in the event of a contingency, during talks on so-called extended deterrence, sources close to the two countries said Saturday.

It is the first time the allies have delved into the issue, in a sign that they are seeking to strengthen the U.S. nuclear umbrella, under which Japan is protected, amid intensifying military activity by China, North Korea and Russia, the sources said.

Japan is the only country to have experienced an atomic bomb attack and has long advocated for a nuclear-free world. However, it also relies on the U.S. nuclear umbrella for defense.

The United States dropped an atomic bomb on Hiroshima on Aug. 6, 1945, and a second one three days later on Nagasaki in the final days of World War II.

As part of the extended deterrence talks in recent years, Tokyo and Washington have held multiple tabletop exercises to strategize a scenario in which a conflict broke out in East Asia and the United States is pressured to use nuclear weapons, according to the sources.

With that in mind, Japan and the United States reviewed how to coordinate and how to deal with issues stemming from the possible use of nuclear weapons, such as managing public opinion. Discussions also broached how much information the United States can share with Japan, the sources said.

ber, the countries announced their first guidelines for extended deterrence — including U.S. nuclear protection — to better tackle regional security challenges.

But details were not revealed due to the sensitivity of information related to national security, according to a senior Japanese Foreign Ministry official.

Diplomatic sources said the guidelines stipulated the steps the countries would take should the United States use nuclear weapons under Article 5 of the bilateral security pact. Article 5 obliges the United States to defend territories under Japan’s administration from armed attack.

The sources close to the nations also said the guidelines made it clear that Japan can convey its thoughts on a possible nuclear weapons use.

Since extended deterrence talks were established in 2010, senior-level discussions, led by top foreign affairs and defense officials, have been held once or twice a year.

The dialogue was upgraded in July 2024, with the first-ever ministerial talks on the issue held in Tokyo to better coordinate the alliance with an eye on China’s military buildup and North Korea’s missile and nuclear development.