Australia, the US and Japan will significantly strengthen defence ties with a quasi-alliance pledge to consult each other over security emergencies in the Indo-Pacific, amid mutual alarm over China’s military build-up and challenge to the international order.

The commitment, announced by Defence Minister Richard Marles with US Defence Secretary Lloyd Austin and their Japanese counterpart Nakatani Gen in Darwin on Sunday, is a step beneath a formal alliance. It means defence officials and political leaders will be locked into consulting over how they respond to events ranging from natural disasters, civil unrest and military actions – including a potential invasion of Taiwan.