The U.S. Defense Department on Tuesday criticized Beijing's assertive activities in waters near the Japanese-controlled, Chinese-claimed Senkaku Islands in the East China Sea, while expressing "support" for Japan on the issue.

"We would urge the Chinese to avoid actions, using their coast guard vessels, that could lead to miscalculation and potential physical...harm," the department's Press Secretary John Kirby said during a press briefing.

File photo taken in September 2012 shows the Senkaku Islands in the East China Sea. (Kyodo) ==Kyodo

"We hold with the international community about the Senkakus and the sovereignty of the Senkakus, and we support Japan obviously in that sovereignty," he added.

The administration of U.S. President Joe Biden, like past administrations, has offered reassurances to Japan that Article 5 of the bilateral security treaty covers the Senkakus, meaning the United States would defend Japan in the event of a conflict there.

China immediately reacted to Kirby's comments on Wednesday, arguing that the islands in the East China Sea are part of the nation's "inherent territory."

"The U.S.-Japan security treaty is a product of the Cold War and it should not harm the interests of third parties and endanger regional peace and stability," Chinese Foreign Ministry spokesman Wang Wenbin told reporters in Beijing, referring to the islets as Diaoyu.

The United States, meanwhile, has taken a neutral position regarding the sovereignty claims.

While Kirby's remarks appeared to back Japan's sovereignty over the islands, another Defense Department spokesperson later clarified that "there is no change to U.S. policy."

In Tokyo, Japanese Foreign Minister Toshimitsu Motegi welcomed the press secretary's comments, saying they were in line with the two countries' shared concerns over Beijing's unilateral attempts to change the status quo in the East China Sea.

"It is extremely deplorable and totally unacceptable that Chinese coast guard ships are entering Japan's territorial waters around the Senkaku Islands repeatedly and making moves to approach Japanese fishing vessels," he said.

The U.S. State Department said last week that the United States joins Japan, the Philippines, Vietnam, Indonesia and other countries in expressing "concern" over a new Chinese coast guard law, saying it may "escalate ongoing territorial and maritime disputes" in the East and South China seas.

Implemented on Feb. 1, the law explicitly allows the Chinese coast guard to use weapons against foreign ships it sees as illegally entering China's waters. Chinese coast guard vessels have been spotted near the uninhabited islets since the law took effect.

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