Australia will seek to boost ASEAN's credentials as the premiere body for maintaining a rules-based order in the region, amid fears it is struggling to keep its focus as members face pressure from China to peel away, at the ASEAN special summit in Sydney this weekend.

As Prime Minister Malcolm Turnbull prepares to welcome leaders of the 10 ASEAN countries, there is a particular concern that pressures are growing for new regional bodies from which Australia may be excluded and that China is using diplomatic manoeuvres over the South China Sea to erode the will of ASEAN countries to take a firm stand on the issue.