Here are some of the key changes expected:

- Counterstrike capacity -

Defence spending will be ramped up to reach the NATO standard of two percent of GDP by fiscal 2027, rising from a traditional level of about one percent.

Some of the money will be for missiles that can be used to destroy enemy launch sites that threaten Japan during an attack -- so-called "counterstrike capacity".

To achieve that quickly, the country is reportedly considering buying up to 500 US-made Tomahawk cruise missiles, as well as a number of long-range SM-6 missiles from Washington.

- Missile upgrades -

Eventually, Japan aims to deploy more than 1,000 long-range cruise missiles able to reach North Korea or coastal areas of China, according to the Yomiuri newspaper.

The nation will likely spend five trillion yen ($37 billion) "to develop and build out its own domestic missile capacity", said James Brady, vice president of Teneo consultancy.

Japanese-developed "extended-range Type-12 (surface-to-ship) missiles, diversified launch platforms, and high-speed glide weapons" could be included in the upgrades, Brady added.

The country is also expected to build around 130 new ammunition depots by 2035 to hold counterstrike missiles and other armaments.

- Southern islands -

To counter threats from an increasingly assertive China, Japan wants to beef up its military presence in its southernmost islands.

The country will reportedly triple the number of military units there equipped with ballistic missile interception capabilities.

According to local media, the government also plans to increase the number of troops stationed in the southern Okinawa region from 2,000 to 3,000.

- Military structure -

Japan's Self-Defense Forces (SDF) will likely be reorganised, with the army, navy and air force placed under a joint command to respond more quickly to emergencies.

For the same reason, the government wants to make it easier for the military to use civilian ports and airports by March 2024, and to strengthen cooperation between Japan's coastguard with the SDF and foreign coastguards.

Japanese officials also want to improve coordination with US forces to better prepare for a potential Taiwan crisis.

There will be new units responsible for drones and another dedicated to cyber warfare as well as improved capacity for information-gathering and responding to high-tech weaponry, such as hypersonic weapons.