Japan's defence ministry on Wednesday unveiled a record $52-billion budget request in a push to maintain military readiness under pressure from China and North Korea.

The military budget has been rising steadily for nearly a decade, with Japan saying it feels threatened by China's vast military resources and territorial disputes, as well as unpredictable North Korea.

Pyongyang has repeatedly tested nuclear devices in recent years, and also missiles -- including some flown over Japan.

The Ministry of Defence is asking for 5.49 trillion yen ($52 billion) for the fiscal year from April 2021, marking nine straight years of increases and a rise from the 5.3 trillion yen for the ongoing year to March.

Among Japan's planned big purchases are two frigates and a submarine, with money also going to the development of a next-generation fighter.

The budget does not include a request for an alternative to the US-developed Aegis Ashore missile interception system, which is intended primarily to protect against possible North Korean attacks.

The Japanese government has scrapped a controversial plan to build the system in two key locations on the main island of Honshu and is now considering putting the interception system at sea -- either by using ships or mega-floats, or by building structures similar to offshore oil rigs.

Japanese defence officials said they cannot attach a price to the system until the government officially decides what to do with it.

Under the planned budget, the defence ministry also said it aims to boost the nation's defensive capabilities in space and cybersecurity, although Japan's progress on those fronts has been slower than other top economies.

Japan's Self-Defence Force plans to launch a new cyber unit with 540 personnel, while a planned space unit will have 70.

It is the first military budget under Prime Minister Yoshihide Suga, who came to power this month by pledging to continue the policies of Shinzo Abe.

Abe steadily sought to expand the role of Japan's military, which is highly circumscribed by the country's pacifist post-war constitution.

But the rising defence spending comes with the world's third-largest economy chronically reliant on borrowed money to finance itself, contributing to public debt that stands at twice the size of its economy.

The government budget is facing particular pressure this year to deal with the coronavirus pandemic.