The first line of protection against invasion by the PRC is the ROC's own armed forces. Current ROC military doctrine is to hold out against an invasion or blockade until the US military responds. There is, however, no guarantee in the Taiwan Relations Act or any other treaty that the United States will defend Taiwan, even in the event of invasion. The joint declaration on security between the US and Japan signed in 1996 may imply that Japan would be involved in any response. However, Japan has refused to stipulate whether the "area surrounding Japan" mentioned in the pact includes Taiwan, and the precise purpose of the pact is unclear. The Australia, New Zealand, United States Security Treaty (ANZUS Treaty) may mean that other US allies, such as Australia, could theoretically be involved. While this would risk damaging economic ties with China, a conflict over Taiwan could lead to an economic blockade of China by a greater coalition.