On Wednesday, McCain called on Japanese Prime Minister Shinzo Abe, Defense Minister Itsunori Onodera and Foreign Minister Fumio Kishida to boost the US-Japanese alliance.

When meeting with Onodera, McCain said he is confident that his colleagues in the US Senate support Japan's position on the islands, Jiji Press news agency reported.

Onodera said Tokyo plans to continue its surveillance of Chinese government ship patrols around the Diaoyu Islands.

Da Zhigang, a Japanese studies researcher at Heilongjiang Provincial Academy of Social Sciences, said McCain is trying to "please some of the Japanese and attract more of the media limelight". Such US politicians are "not expecting either a peaceful resolution of the islands dispute or a stable Asia-Pacific region", he said.

McCain also voiced support for the Japanese Cabinet's plan to revise their country's pacifist Constitution, a move aimed at lifting restrictions on Japan's armed forces.

Some of Tokyo's policymakers have been trying to deny the country's militarist past in World War II, and Japan is seeking an assertive military buildup, which has "worried international players, including the US", said Xu Dunxin, former vice-minister of foreign affairs.

"If someday Japan goes off the peaceful path, I think even the US, its traditional ally, will not allow that to happen," said Xu, who also served as Chinese ambassador to Japan.

McCain's remarks are sending a motivating signal to radical Japanese right-wing forces, and also "totally missing the bigger picture of the Sino-US relationship", Ruan said.

The Sino-Japanese relationship was greatly strained after the Japanese government unilaterally announced the "nationalization" of the Diaoyu Islands in September.