US Defense Secretary Lloyd Austin was scheduled to announce an enhancement of the US command structure in Japan on Sunday, as Washington and Tokyo revamp military cooperation to counter China's rapid development.

The US currently has about 54,000 military personnel in Japan who report to the Indo-Pacific Command in Hawaii, which is approximately 6,500 kilometers away and 19 hours behind. However, Austin, along with US Secretary of State Antony Blinken, who was attending "2+2" talks with Japanese counterparts in Tokyo, was expected to reveal the establishment of a new Joint Force Headquarters led by a three-star commander, according to a US military official.

This new command will align with Japan's planned Joint Operations Command for all its armed forces, enhancing the agility of both militaries in the event of a crisis involving Taiwan or the Korean peninsula.

The discussions between Japan and the US were also set to explore the development of Washington's "extended deterrence" commitment, which includes using military capabilities, such as nuclear weapons, to defend Japan.

According to Naoko Aoki, a political scientist at the RAND Corporation, Japan has been unsettled by China's military modernization, DPRK's nuclear and missile activities, and nuclear threats observed during the Ukraine war.

Speaking with AFP, Aoki stated, "[It] is important for the United States to reassure Japan of its commitment and signal to potential adversaries that the alliance remains strong and that the United States is committed to using nuclear weapons if necessary to defend Japan." 

On Monday, Blinken and Japanese Foreign Minister Yoko Kamikawa will meet with their Indian and Australian counterparts, S. Jaishankar and Penny Wong, as part of the Quad alliance, which is viewed as a counterbalance to "China's influence".

Nuclear weapons included in methods US will vow to use to defend Japan

This comes after a bilateral meeting between both nations decided to draft their first joint document on expanded deterrence policy, which will include a clause affirming the United States' commitment to defend Japan by various means, including nuclear weapons, Japanese newspaper Yomiuri Shimbun reported, citing sources.

The document, as per the newspaper, will outline both nations' positions on implementing deterrence policy and will specify the US determination to enhance regional deterrence for Japan, detailing the measures Washington can employ in both peacetime and potential emergencies.
 
The document will also detail the scenarios under which the United States can retaliate against third countries on behalf of Japan and outline potential responses, according to the newspaper.

In 2010, the Japanese and US governments created the Extended Deterrence Dialogue to explore methods for maintaining and enhancing extended deterrence. They began to hold regular consultations on this matter, involving officials responsible for foreign policy and defense affairs.