BEIJING -- China has permitted rare street protests and sent armadas of fishing boats to show its growing national interest in a small string of islands in the East China Sea. Earlier this year, the Chinese military locked its radar on a Japanese navy vessel.
Each step seemed like a measured escalation in the long-running territorial dispute, intended to press Japan to negotiate over jurisdiction of the islands. But they also seemed calibrated to avoid a sharp international backlash -- or to raise expectations too high at home.
But by imposing a new air defense zone over the islands last weekend, Beijing may have miscalculated. It provoked a quick, pointed challenge from the U.S., set off alarm bells among Asian neighbors and created a frenzy of nationalist expression inside China on hopes that the new leadership team in Beijing would press for a decisive resolution of the long-standing dispute.
On Wednesday, hours after the Pentagon sent two B-52 bombers defiantly cruising around China's new air defense zone for more than two hours, Beijing appeared to backpedal. The overflights went unchallenged, and some Japanese civilian airlines ignored China's new assertion of air rights.
"We will make corresponding responses according to different situations and how big the threat is," the spokesman at the Foreign Ministry, Qin Gang, said when asked about China's lack of enforcement against the U.S. planes.
The issue is likely to come up when Vice President Joe Biden meets with Chinese leaders in Beijing next week.
Mr. Biden will use meetings to express U.S. concern about China's behavior toward its neighbors and seek an explanation of the air zone it has claimed over disputed areas of the East China Sea, according to an administration official who briefed reporters Wednesday on condition of anonymity to discuss the vice president's plans.
Under President Xi Jinping, China has suggested that it intends to make a more robust defense of its national interests, including in maritime disputes, to match its rising economic and military power. But even some Chinese analysts say they wonder whether the new leadership team fully anticipated the response to the latest assertion of rights -- or had in mind a clear Plan B if it met with strong resistance.
China does appear determined to escalate the issue of the uninhabited islands, known as Diaoyu in China and the Senkaku in Japan, as a way of forcing the Japanese to negotiate and give up control of territory that has symbolic and strategic value for both countries. In the long term, China has not tried to disguise its goal of weakening the alliance between the U.S. and Japan and supplanting the U.S. as the dominant naval power in the Western Pacific.
Beijing is especially frustrated that its previous, more cautious steps to convince Japan of the seriousness of its claim to the islands has not prompted Japan, which administers them, to negotiate in earnest.
"Japan always has the backing of the United States and shows unbelievable arrogance to the Chinese proposal to have talks on a bilateral basis," said Zhu Feng, a professor of international relations at Beijing University and one of China's more moderate voices on Japan. "Japan's arrogance is unacceptable."
But if China has been trying to drive a wedge between Washington and the Japanese government of Prime Minister Shinzo Abe, their strategy seems to have backfired, at least for now.
The U.S. had for months seemed reluctant to get involved or take sides in a dispute that carries so much emotional weight for China. U.S. officials complained that some Japanese leaders had made nationalist gestures that antagonized China, worsening the tensions. And the Obama administration dodged requests by Japanese leaders to take a clearer stance in their favor.
That hesitation seems to have vanished since China pronounced that it was expanding its hold on the region's airspace.
With the flyover by the B-52s, the U.S. has shown that it is more willing to work with Japan in opposing China's efforts to force a change in the status quo, even if the U.S. still takes a neutral stance in the islands dispute itself. Hours after China declared its new air zone, Defense Secretary Chuck Hagel reaffirmed that the U.S. would stand by its security treaty obligations to aid Japan if it were attacked.
Tokyo has also emphasized its ties with Washington.
On Wednesday in Tokyo, the defense minister, Itsunori Onodera, pledged in a phone call with Mr. Hagel to work closely with the U.S. military by sharing information and coordinating in the surveillance of Chinese activities in the East China Sea, Japan's Defense Ministry said.
Bloomberg News contributed.