BEIJING (AP) — China on Wednesday called the Japan-U.S. mutual security pact a product of the Cold War following U.S. criticism of the presence of Chinese coast guard vessels in Japanese-claimed territorial waters over the weekend.

Foreign Ministry spokesperson Wang Wenbin also reasserted China’s claim to a string of tiny, uninhabited islands in the East China Sea controlled by Japan.

The verbal exchange followed reports that two Chinese coast guard ships on Sunday twice entered Japanese territorial waters surrounding the islands, known by Japan as Senkaku and by China as Diaoyu.

Chief Pentagon spokesperson John Kirby on Tuesday said China had “continued to flout international rules” and the U.S. would work with its allies to address such challenges.

Wang did not directly address the criticism but said the islands were “China’s inherent territory.”

“The U.S.-Japan security treaty is a product of the Cold War, which should not harm a third party’s interest or endanger regional peace and stability,” Wang said at a daily briefing. China has long accused those who challenge its behavior as maintaining a “Cold War mentality.”

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The 1960 security treaty assures the U.S. would come to Japan’s aid in the event of an outside attack on Japanese forces or territory.

Japan has also protested Sunday’s incident, in which the Chinese ships attempted to approach a Japanese fishing boat, prompting intervention by a Japanese patrol.

Japan’s coast guard said it was the ninth time this year that Chinese coast guard ships have entered Japanese territorial waters around the islands.

China last month passed a new law authorizing its coast guard to fire on foreign vessels and destroy structures on features it claims. That has raised concerns around the region that China may become more inclined to use force to assert its claims in the East China and South China seas.