China reportedly warned that Japan would "cross a red line" by sending Self-Defense Forces to join U.S. operations in the South China Sea.
Chinese Ambassador Cheng Yonghua told a high-ranking Japanese official in June that Japan should not send Self-Defense Force ships to join U.S. operations in the South China Sea, according to a report published in the Japan Times over the weekend, and also hinted at military action.
Cheng gave the warning before an international tribunal rejected China’s contested territorial claims in the South China Sea and ruled that they have no legal or historical basis. China has dismissed the ruling, which was handed down on July 12. The United States and Japan have, meanwhile, urged Beijing to accept it.
The U.S. Navy has on multiple occasions since October sailed warships near manmade islands China has constructed in the South China Sea to exercise America’s right to freely navigate through international waters, drawing ire from Beijing. The U.S. and Japan have both objected to China’s military buildup on islands in the South China Sea.
Japan does not intend to send warships to join freedom of navigation exercises with the U.S. but could send Self-Defense Force vessels to protect American ships in the waters under new security laws.
The Japan Times reported:
According to the sources, Cheng told the high-level official in Tokyo that Japan should not take part in a "joint military action with U.S. forces that is aimed at excluding China in the South China Sea." He also said China "will not concede on sovereignty issues and is not afraid of military provocations." The comments were apparently aimed at preventing Tokyo from interfering in the territorial dispute in the South China Sea, where Japan has no direct claims. The official told Cheng that Japan has no plans to join the U.S. operations but strongly criticized China’s construction of outposts in the waters for military purposes.
Tensions between China and Japan have risen recently because of a dispute over claims to islands in the East China Sea. Japan has increasingly seen Chinese Coast Guard and government ships near the islands, which are called the Senkaku Islands in Japan and the Diaoyu Islands in China.
Earlier this month, Japan’s Foreign Minister Fumio Kishida phoned Cheng multiple times to warn him that the countries’ ties were "deteriorating markedly" over the dispute.