Washington and Canberra have a number of diplomatic and economic weapons at their disposal right now to counter Chinese coercion and form a Taiwan contingency coalition. 
These instruments can be used by the US and Australian leaders to build a broader global consensus in favour of Taiwan’s defence, deeper ties with Taipei, maintain the international status quo, and clearly communicate the costs of military action against Taiwan to China.
The Quadrilateral Security Dialogue members—Australia, India, Japan, and the United States—should begin by clarifying the group’s military commitments in the region.

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