JAKARTA — China’s intensifying move to assert claims over the South China Sea has given fresh impetus to a military build-up in Indonesia that will see its forces deployed with greater focus on external risks.

After years of concentrating on separatist threats, Indonesia plans to deploy attack helicopters to its islands at the southern end of the South China Sea and expand its naval power. The front-runner for July’s presidential election, Mr Joko Widodo, aims to boost defence spending to a 1.5 per cent share of the economy.

The strategy shift comes as China escalates disputes with the Philippines and Vietnam, fellow members of the Association of South-east Asian Nations. China’s standoff with Vietnam over an oil rig this month followed its 2012 success in taking control of the Scarborough Shoal from the Philippines.

“The focus in defence spending is moving to dealing with external threats,” said Mr Tim Huxley, executive director of the International Institute for Strategic Studies in Singapore. “There is a concern … that the South China Sea should not become a Chinese lake and that freedom of shipping should be maintained.” That is influencing Indonesia’s defence spending and procurement, he said.

The military is about 40 per cent of the way to developing a minimum-essential force, or MEF, by 2029, to guard its territory as it adds tanks, submarines, helicopters and jet fighters to its arsenal, Deputy Defence Minister Sjafrie Sjamsoeddin said in an interview.

Under the MEF, the government is seeking to acquire 274 Navy ships, 10 fighter squadrons and 12 new diesel-electric submarines.

“We’re part of maintaining regional stability and peace, and to maintain that we must certainly have powers that support that regional strength,” Mr Sjamsoeddin said.

Indonesia has sought to stay out of its neighbours’ spats with China over the South China Sea, and is not an official claimant to areas in dispute. But it recently said that China’s interpretation of its nine dash-line map — the basis for its territorial claims — is seeping into Indonesia’s exclusive economic zone.

Commodore Fahru Zaini, assistant deputy to the chief security minister for defence strategic doctrine, said in March that China’s map included an “arbitrary claim” to waters off the Natuna Islands in the Indonesian province of Riau.

Indonesia will deploy four Boeing Apache attack helicopters to the Natuna Islands, IHS Jane’s reported in March, citing the army’s chief of staff.

With China more assertive in the southern part of the South China Sea, “the Indonesian armed forces are strengthening their military presence on the Natuna Islands, and that includes preparing facilities on the Natuna Islands to accommodate jet fighters”, said Mr Ian Storey, senior fellow at the Institute of South-east Asian Studies in Singapore.

“During the first decade of this century they were focused on combating internal threats, that is, separatism and terrorism. But they’ve been largely successful in containing those threats and I think now they’re focusing more outwards, focusing on external threats.” BLOOMBERG