TOKYO - The United States on Sunday announced plans for a major revamp of its military command in Japan to deepen coordination with its ally's forces.

The announcement followed security talks in Tokyo between US Secretary of State Antony Blinken and Secretary of Defence Lloyd Austin and their respective Japanese counterparts, Yoko Kamikawa and Minoru Kihara.

"The United States will upgrade the US Forces Japan to a joint force headquarters with expanded missions and operational responsibilities," Austin told reporters after the so-called "2+2" talks.

"This will be the most significant change to US Forces Japan since its creation and one of the strongest improvements in our military ties with Japan in 70 years."

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The ministers said in a joint statement that the new command structure would be implemented in parallel with Tokyo's own plans to establish a joint command for its forces by March 2025.

Japan provides a base for the US to project military power in Asia, hosting 54,000 American troops, hundreds of US aircraft and Washington's only forward-deployed aircraft carrier strike group.

Japan has in recent years shifted dramatically from decades of postwar pacifism. In 2022 it unveiled a plan to double defence spending to 2 percent of gross domestic product.

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The new US command in Japan will be headed by a three-star general, a US official said, however Austin said the US would not rule out appointing a four-star commander to Japan in the future as it has in neighboring South Korea.

For the first time, the ministers also discussed "extended deterrence", a term used to describe the US commitment to use its nuclear forces to deter attacks on allies.

It is a sensitive subject in Japan, which has pushed for non-proliferation of nuclear weapons and is the only country to have suffered atomic bomb attacks.

The countries discussed reinforcing extended deterrence to promote regional stability and deter the outbreak of conflict, according to an official readout that was scant on detail.

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"I welcome the continuously deepening discussion on this matter," Japan's Kamikawa told reporters at the outset of the talks.

Austin and Kihara also met South Korean Defence Minister Shin Won-sik, signing an agreement to "institutionalize" trilateral cooperation in matters of joint military exercises, among other things.