Being President Barack Obama's emissary is a tough job these days.

While Secretary of State John Kerry struggles unsuccessfully to make any impression on Russia, Israel, Palestinian leader Mahmoud Abbas or a Saudi Arabian government that thinks the U.S. has gone off track in the Middle East, Defense Secretary Chuck Hagel had a similarly difficult time with China.

Secretary Hagel went to China last week, acknowledging that in the view of the Obama administration China is a "great power." But his reception, while polite, was anything but encouraging.

The Chinese let him tour their new aircraft carrier, then announced that they will continue to insist on territorial claims in the South China Sea. That despite Mr. Hagel's earlier assertion in Japan that "you cannot go around the world and redefine boundaries and violate territorial integrity and sovereignty of nations by force, coercion or intimidation, whether it's in small islands in the Pacific or in large nations in Europe."

Mr. Hagel said the U.S. stands behind Japan's long-standing claim to the Senkaku Islands, while China's textbooks teach that the same islands, called Diaoyu, have been Chinese from time immemorial. The uninhabited islands may have oil resources.

The Chinese answer, delivered last Tuesday by Defense Minister Chang Wanquan: "We will make no compromise, no concession, no trading, not even a tiny ... violation is allowed."

Mr. Chang said President Obama's promise to shift more military resources to Asia was aimed at "containing" China, and told reporters China "can never be contained." He criticized Japan, the Philippines and Taiwan for making claims to territory and seabed resources he claimed for China, and criticized the U.S. for selling arms to Taiwan.

Though Mr. Chang did generously add that the Pacific is big enough to contain the ambitions of China and the U.S., his core message was unmistakable: Not in China's backyard. Given that China claims that its backyard contains some of the world's most important shipping lanes and that it aggressively pushes an expansionist view of its rights in the area, a conflict with neighbors who have relied on the U.S. since World War II to maintain freedom of navigation in the area seems inevitable.

The U.S. and China did agree on some new military-to-military discussions and a joint humanitarian-aid exercise at some undefined future date.

But it is hard to escape the impression that China thinks America's power is waning, giving it the opportunity to push for domination of the Asian coastlands.