No wait. We already got that messsge from the US State Department in the 1960s (not a criticism, as naturalman has pointed out, there are some things the treaties do not cover - and when they don't, support is not automatic)
Unless Australia had stated both that it would militarily support East Timor and that Australia considered China to be a longtime ally, your analogy to Foreign Minister Downer's statement to U.S. statements from the 1960's is inapplicable.