Tokyo and Beijing are hostages to Chinese public opinion in a spat over disputed islands that shows no sign of ending, analysts say, warning the longer it goes on, the higher the chances of the situation escalating out of control.

And Taiwan's forceful entry into the fray over the Japanese-controlled archipelago this week serves to underscore how isolated Tokyo has become, with its forlorn hope that Washington will one day ride to the rescue.

A meeting of Japanese and Chinese foreign ministers on the sidelines of the UN General Assembly in New York late Tuesday was described as "severe" and appeared to have achieved little towards easing tensions.

A major obstacle, said Mitsuyuki Kagami, professor of Chinese political thought at Japan's Aichi University, is that the Chinese leadership has been backed into a corner.

"China's top leaders have been trying to contain hawkish factions in the Communist party and the military, but nationalist fervour has now reached a point where it is not easily controllable," he said.

The country's military had been revving up for a robust response to Japan's impending nationalisation of what Tokyo calls the Senkakus and Beijing knows as the Diaoyus, he said.

Political leaders had been able to keep a lid on this, even after Japanese nationalists planted their flag on one of the islands in August.

President Hu Jintao and leader-in-waiting Xi Jinping "remained silent on the disputes until the September 9 meeting" between Hu and Japanese Prime Minister Yoshihiko Noda on the sidelines of the Asia-Pacific Economic Cooperation summit, he said.

"But Japan made Hu lose face, because just two days after he protested Tokyo's planned nationalisation in a comment widely reported in China, Japan went through with the act."

The Chinese leadership now fears that unless they can come away from the fight having won concessions from Japan, they will look weak and public anger currently directed at Tokyo will turn on them, he said.

Beijing-based Stephanie Kleine-Ahlbrandt, Northeast Asia project director at the International Crisis Group, writing in Foreign Policy earlier this month said rising nationalism in China, which has seen sometimes violent protests against Japan "restricts China's future options to dial down the situation".

"For all the government's efforts at censorship and control, the Internet has given the Chinese public unprecedented access to information (and) commentary, eroding Beijing's control over the ebb and flow of nationalist sentiment.

"Internet users can now track Chinese law enforcement vessels via satellite photos, mocking and criticising the government when they stop short of disputed waters," she wrote.

A duel with water cannon near the islands on Tuesday when Japan's coastguard confronted dozens of Taiwanese fishing boats that were accompanied by official coastguard ships was a worrying turn for Tokyo, said Thomas Berger, a specialist in international relations at Boston University.

Taiwan's involvement "is profoundly troubling" as "it underlines Japan's growing isolation in the region", he said.

Japan is also involved in a battle with South Korea over the ownership of a different set of islands in the Sea of Japan, a stretch of water Koreans know as the East Sea.

"The only resource Japan feels it has left is the United States, and Japanese expectations that the US will come to its rescue are rising rapidly. So too is the potential for disappointment," said the East Asia specialist.

Washington faces a dilemma over the issue as it "does not want to encourage reckless Japanese behaviour or damage already strained Sino-US ties.

"At the same time it cannot maintain a geo-strategic presence in Asia, and thus hedge against China's becoming an expansionist power, without Japan," he said.

China is pushing for a "new normal" around the disputed islands, where its official ships can come and go with impunity, said Kagami.

And the increased frequency of Chinese patrols that this entails, along with a continuing Japan Coast Guard presence raises the chance of something going awry, said the ICG's Kleine-Ahlbrandt.

"Although the two countries have dealt with past run-ins -- such as when the Japanese Coast Guard arrested a Chinese skipper in 2010 after his boat collided with a Japanese vessel -- and succeeded in cooling tensions, the current situation is of a different order," she wrote.

"That act could be attributed to an overzealous Chinese fisherman. But now, a skirmish between official law enforcement vessels in the current context could prove irresolvable."