Japan's Prime Minister Fumio Kishida instructed ministers on Monday to boost the country's defence budget by 56 percent over the next five years to $318 billion.
The government is overhauling its defence and security strategies in response to regional threats from nuclear-armed North Korea and an increasingly assertive China.
Defence Minister Yasukazu Hamada said Kishida told him that "the size of the medium-term defence programme for the next five years, which is currently being arranged, should be around 43 trillion yen ($318 billion)".
"This is a level at which we can achieve the goal of strengthening our defence capability," Hamada told reporters after talks with Kishida and the finance minister.
The amount would be more than 1.5 times larger than the current five-year spending plan of 27.5 trillion yen.
The decision comes a week after Kishida announced he wanted to increase defence spending to two percent of GDP by 2027.
For decades, Japan has spent around one percent of GDP or less on defence, less than the NATO standard of two percent.
But growing pressure from China, including military exercises and the presence of boats around disputed islands, has helped build support for a bigger budget.
The war in Ukraine and repeated missile launches by North Korea have also sharpened views.
The move is controversial in Japan for several reasons, however, including the country's post-war constitution which limits its military capacity to ostensibly defensive measures.
Japanese media reports say one target of additional spending would be "counterstrike" capacity -- weapons that can target enemy missile launch sites and described by Tokyo as defensive.