Senators Benjamin L. Cardin and John McCain will soon get their wish for a U.S. arms sale to Taiwan. Last Wednesday, Josh Rogin of Bloomberg View reported that the Obama administration will formally announce a $1 billion arms sale in December. Congress has not been notified of a new arms sale to Taiwan in four years.

The changing balance of power in the Taiwan Strait warrants a serious examination of the existing U.S.-Taiwan security relationship, which is held up by two pillars: a U.S. commitment to sell “defensive” arms to Taiwan; and the pledge to take “appropriate action” in response to any “threat to the security…of the people on Taiwan.”

The arms sales and vague security pledge have contributed to peace in the Taiwan Strait, but the status quo may not last much longer. A recent RAND report concluded that China is catching up to the United States’ military capabilities to defend Taiwan. America could absorb the rising cost of defending Taiwan, but the reunification of Taiwan and mainland China is a core interest of the Chinese government. Since China has more at stake, it has an incentive to keep raising the costs of confrontation until the United States is no longer willing to absorb them. 

This argues for dropping Washington’s pledge to come to Taiwan’s aid. Supporters of the pledge worry about the message that a reduced commitment would send to allies in East Asia. But there is a significant difference between a formal security commitment defined in a treaty, and an informal one like America’s to Taiwan.

Washington’s formal treaty commitments in East Asia (Japan, South Korea, and the Philippines) are more clearly stated and some are supported by forward-deployed U.S. forces. Failing to come to the aid of a formal treaty ally would be a significant blow to U.S. credibility, but Taiwan does not enjoy such status.

However, arms sales to Taiwan should continue for several reasons. First, the arms sales have not significantly damaged U.S.-China relations. Second, ending both arms sales and the pledge would be unnecessarily disruptive. Third, the United States still has a legitimate interest in a peaceful resolution of the cross-strait dispute, but defending Taiwan’s quasi independent status through military intervention against a nuclear-armed and conventionally powerful China would have high costs for limited benefits. Moreover, the costs of intervention would likely increase over time, while the benefits would remain flat. 

Future arms sales should emphasize weapons systems that allow Taiwan to mount an effective asymmetric challenge to Chinese forces. The United States should also make future arms sales contingent on Taiwan’s investment in indigenously-produced capabilities and increased military spending independent of spending on U.S. arms. Ending the already vague pledge to come to Taiwan’s defense while continuing arms sales is a low-cost policy that reduces the probability of a U.S.-China war over Taiwan while preserving Taiwan’s ability to defend itself.