Chinese paramilitary policemen run past bottles thrown by demonstrators during a protest over the Diaoyu islands issue, known as the Senkaku islands in Japan, outside the Japanese Embassy in Beijing last year. (MARK RALSTON/AFP/GETTY IMAGES)

BEIJING — Judging by some of the commentary in the Chinese media, an outside observer might think war with Japan is imminent. “The Chinese military could win a war over the Diaoyu Islands in half an hour,” Major General Zhang Zhaozhong, a Chinese military scholar, was quoted as saying last week.

Chinese hawks are not the only ones raising the spector of a military clash between Asia’s two largest economies. Since Tokyo infuriated Beijing last September by nationalizing some of the disputed Senkaku Islands, known as the Diaoyu in China and Taiwan, tensions between the two countries have escalated.

Both militaries regularly fly fighter jets in the airspace above the islands and have scrambled them against each other.

Japan’s coast guard on Monday cited three Chinese vessels in waters near the islands. In response to warnings to leave the area, the Chinese ships broadcast messages over loudspeakers in Japanese and Chinese stating, “This is historically Chinese territory.”

It is the latest in a series of bellicose exchanges that some observers fear could lead to a clash.

“There is indeed a risk of an accident, although the possibility that it could escalate further into a full-scale conflict is very, very small,” said Huang Dahui, a professor at Renmin University in Beijing.

In the U.S., which could see itself dragged into a conflict as Japan’s military ally, diplomacy has moved up a gear in recent days. Kurt Campbell, assistant secretary of state for east Asian and Pacific affairs, said on a visit to Tokyo last week: “We’ve made very clear our desire to see cooler heads prevail.”

The U.S. was criticized by Beijing on Monday after Secretary of State Hillary Clinton, secretary of state, argued last week that Washington opposed “any unilateral actions that would seek to undermine Japanese administration” of the islands.

“The U.S. bears undeniable historical responsibility,’’ for the situation, Hong Lei, Chinese foreign ministry spokesman, was quoted as saying.

Washington, anxious to avoid a confrontation with China so early in the tenure of Xi Jinping, the ruling Communist party’s new leader, has told Japan not to give China an excuse to overreact.

But Japan also has a new leader and both Shinzo Abe, prime minister, and Xi will fear that showing weakness could damage them domestically.

In China, the military and a nationalist public hope that Xi, who is expected to lead the world’s most populous country for the next decade, will assert China’s interests more forcefully than Hu Jintao, his predecessor.

The Chinese government has seized on Tokyo’s nationalization move to cement its own claim to the Senkakus with a series of legal, administrative and military moves.

In Japan, the Liberal Democratic party and its nationalist leader, Abe, won a landslide election in December after a campaign which promised a tougher stance on China.

Abe has quietly dropped a campaign proposal to station civilian government officials on the islands but risks alienating conservative supporters if he fails to respond to perceived Chinese provocation.

Japanese authorities also fear that if they don’t challenge China, Beijing could present Japan’s passivity as evidence of a lack of control over the islands.

Already, Beijing has called on Tokyo to recognize a change in the status quo. Echoing that stance, Liu Jiangyong, an international relations expert at Tsinghua University, claims that “the Diaoyu islands are by no means exclusively controlled by Japan.”

Since taking office, Abe has called for more defense spending and initiated a program of regional diplomacy that looks aimed squarely at countering China.

At the same time, advisers in Beijing and Tokyo insist the governments want to de-escalate, but are struggling over how to lower tensions.

Kuni Miyake, a former Japanese foreign ministry official and now a visiting professor at Ritsumeikan University in Kyoto, believes any climbdown would have to be negotiated secretly. “There is a face issue involved, and neither side wants to be the one to initiate [a de-escalation].”

One step Tokyo might take would be to abandon its official position that no territorial dispute exists. People close to the government say Japan might accept adjudication by the International Court of Justice, but only if China requests it.

“The Chinese government will not do that,” said a person who has been advising the government on relations with Japan. “Japan has had actual control of the islands for a long time, and that would not be in China’s favor.”

— Financial Times

Geoff Dyer in Washington and Zhao Tianqi also contributed to this report.