American and Asian strategic thinkers are beginning to use terms like "entrapment" and "abandonment" to reflect contrasting concerns over U.S. defense commitments in the Asia-Pacific.

The entrapment problem is occasioned by American worries that longstanding security arrangements could drag the United States into a Chinese-Japanese, Chinese-Taiwanese or Chinese-Filipino conflict.

“Entangling alliances” concerns also work in the other direction. Some Japanese fear being pulled into a U.S.-Chinese confrontation over Taiwan. South Koreans want no part of a Japanese-Chinese clash over disputed islands that would invoke Washington’s treaty commitments to Tokyo. Even loyal ally Australia harbors misgivings about sacrificing economic relations with China to meet security obligations to the United States.

On the flip side, there is the abandonment problem. Observers in Japan, Taiwan and the Philippines fear that Washington’s deference to China might weaken U.S. security commitments to them. They see America’s war-weariness, financial constraints and problematic history in Asia.

Beijing appeals to both sets of impulses to undermine America’s security relations. It sows Asian doubts about U.S. will and staying power while conveying a sense of inevitable Chinese regional dominance. It accuses Washington of emboldening reckless behavior from its security partners and then exploits any partner’s misstep as provocative conduct that will draw the U.S. into conflict. Beijing’s message: collective security really means collective endangerment.

While core U.S. defense commitments—a Chinese and/or North Korean attack on Japan and/or South Korea—are not in doubt, other scenarios may challenge Washington’s reliability as a security partner.

Taiwan

The standoff across the Taiwan Strait is the longest-continuing flash point threatening Sino-U.S. conflict. Without the 1954 defense pact that President Carter abrogated in 1979, U.S.-Taiwanese security arrangements are governed by the Taiwan Relations Act.

The TRA obligates the United States to provide defensive weapons to Taiwan and declares that any nonpeaceful effort to determine its status would be a matter “of grave concern to the United States.” But it does not formally commit Washington to defend Taiwan. And therein lies the special Taiwan danger: strategic miscalculation by Beijing.

Successive American presidents have adopted the Clinton administration’s ambiguous hedging language on the defense of Taiwan: “it would depend on the circumstances.” In 2001, President Bush briefly dabbled with strategic clarity, pledging to do “whatever it took” to defend Taiwan—but alarmed China hands quickly walked that back. After September 11, China was declared a strategic partner in the war on terror and Taiwan remained an irritant to Sino-U.S. relations.

Last year, a former high-ranking official was asked if the United States would defend Taiwan against a Chinese attack and responded: “That’s what it’s useful for them to believe.” Has subtle strategic ambiguity become blatant strategic coyness?

Lacking a clear American security pledge, some Taiwanese advocate enhancing Taiwan’s own retaliatory capabilities against China. Others favor reducing military spending and cutting a political deal with Beijing before Taiwan’s 2016 presidential election. American officials find both outcomes problematic.

Taking advantage of the U.S.-Taiwanese policy muddle, China has built antiaccess and area-denial weapons to deter or delay a U.S. defense of Taiwan. Those Chinese attack submarines and antiship ballistic missiles are the new “circumstances” Washington’s ambiguity policy invited Beijing to create. The policy and the weapons may well be tested in the “actual combat” Xi Jinping recently told his military to practice.

Scarborough Shoal

In April 2012, Chinese maritime-surveillance vessels and Filipino navy ships faced off over disputed fishing reefs in the South China Sea near the Philippines coast. As with other regional maritime disputes, Washington takes no position on the competing claims but insists on peaceful resolution and navigational freedom. It mediated a face-saving way out: the two sides agreed to withdraw their ships, then negotiate their claims. The Philippines complied, but China reneged, sending more ships and placing a rope barrier to exclude Filipino fisherman from their traditional fishing grounds.

Neither the Philippines nor the United States have directly challenged China’s defiant actions, but Manila took the matter to a United Nations Law of the Sea tribunal. Presently, the U.S. and Philippines navies are conducting long-planned joint exercises in the area pursuant to their mutual-defense treaty.

Senkaku Islands

After World War II, Japan was granted administrative control over the Senkakus, which China also claims as the Diaoyu. Again, the United States is agnostic on ultimate sovereignty as long as the issue is settled peacefully and does not threaten freedom of navigation.

Significantly, however, Secretary Clinton stated last year that the Senkakus are covered by the U.S.-Japanese mutual-defense treaty, thus raising the stakes for China. Some U.S. policy experts believe the U.S. commitment goes too far and risks U.S.-Chinese conflict over a useless “pile of rocks.”

Such statements by U.S. experts, however unofficial, raise Japanese fears of U.S. abandonment. Conversely, some in Japan want facilities constructed on the islands, triggering U.S. fears of provoking China. Others advocate consideration of Japan’s own nuclear deterrent. That idea may gain support after President Obama’s call for further reductions in the U.S. nuclear stockpile as North Korea and China continue adding to their own arsenals.

Each of America’s security partners wants its own U.S. commitment but fears the spillover of commitments to others. It will take wise and steady Washington leadership to avoid the Scylla of entrapment and the Charybdis of abandonment.

Joseph A. Bosco served as China country director in the Office of the Secretary of Defense, 2005-2006, and is presently a member of the U.S.-China task force at the Center for the National Interest .