Australia's prime minister says his country will bolster its naval strength with more submarines and warships as part of a long-term military buildup needed to maintain peace in the Asia-Pacific region.

Prime Minister Malcolm Turnbull said Thursday that Australia plans to double the size of its submarine fleet to 12 as well as commissioning three additional air warfare destroyers, nine anti-submarine frigates and 12 patrol boats.

The naval increase is at the center of a planned 20-year military buildup to deal with future threats, including tensions in the South China Sea where China, Australia's most important trade partner, is aggressively staking territorial claims.

The plan says the United States will remain the pre-eminent global military power and will continue to be Australia's most important strategic partner.