Combined regional defence budgets will grow from USD 435 billion last year to USD 533 billion in 2020, furthering a shift in global military spending away from Western Europe and North America toward emerging markets, especially in Asia, the report said.
"A number of the South China Sea's littoral states appear to be responding to China's more assertive stance in the region and there is no sign of this trend coming to an end," Janes' principal analyst, Craig Caffrey, said in the report.
Following years of double-digit annual percentage increases, China has far-and-away the region's biggest defence budget at USD 146 billion last year, according to the government.
That growth is now slowing and Jane's said it expects China's budget to rise by about 5 per cent to USD 233 billion by 2020.
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Over recent years, Beijing has created new islands and built airfields and other military infrastructure on them, although Beijing says they are intended largely for civilian use.
While China says it has no objections to freedom of navigation in the area, it has frequently interfered with or issued warnings to fishing vessels and military planes and vessels.