China's top diplomat in Australia has declared Beijing is prepared to "fight to the end" in its trade war against Donald Trump to protect its privileges and concessions, while also offering a full-throated defence of its Communist leadership.

As Prime Minister Scott Morrison in a speech in Sydney signalled support for some of Mr Trump's grievances ahead of the crucial G20 leaders summit in  Japan, Ambassador Cheng Jingye told a business audience in Canberra China was strong enough to withstand a protracted fight.