China is “gravely concerned and indignant” over Japan’s plans to step patrols in the South China Sea.

In a regular scheduled press conference on Friday, Chinese foreign ministry spokesperson, Hong Lei, warned Japan to stay out of the South China Sea dispute.

“The Chinese side is gravely concerned and indignant about the negative moves of the Japanese side. We have lodged multiple solemn representations with Japan,” Hong stated.

He went on to say:

Japan is not a party concerned to the South China Sea issue. Recently it has behaved in an abnormal way, deliberately thrust a hand in the South China Sea issue, driven a wedge among regional countries and maliciously created tensions in the South China Sea. Japan’s moves do no good to solve the South China Sea disputes, or safeguard peace and stability of the South China Sea. It also severely damages the political and security mutual trust between China and Japan, and runs counter to the momentum of improving bilateral relations. We once again urge the Japanese side to abide by its commitment of not taking sides on the South China Sea disputes, put an immediate end to the hyping up of the South China Sea issue and groundless accusations against China, stop provoking conflicts among different parties for self-serving interests, genuinely maintain the momentum of improving Sino-Japanese relations and respect the efforts by China and ASEAN countries to safeguard peace and stability of the South China Sea.

The spokesperson’s comments come on the heels of Japan’s Maritime Self-Defense Forces announcing it will hold a joint military exercise with the Philippines in the South China Sea later this month.

“We will announce the details such as the schedule and assets we will send as soon as the plan is fixed,” Tomohisa Takei, chief of staff for the Maritime Self-Defense Force, told Japanese reporters earlier this week. Nonetheless, Japanese media outlets have reported that Tokyo will dispatch a P3-C Orion patrol aircraft for the exercise.

Last month, Japan sent two destroyers to the South China Sea to hold a one-day exercise with the Philippines, which reportedly had one of its newest warships participate. That exercise took place just 300 kilometers away from the Scarborough Shoal, which China seized from the Philippines in 2011.

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The United States strongly backs Japan’s participation in the South China Sea, and in fact has reportedly proposed joint U.S.-Japanese patrols in the area.

In an interview with Reuters earlier this year, Admiral Robert Thomas, America’s top naval officer in the Western Pacific, said that "I think that JSDF (Japan Maritime Self Defense Forces) operations in the South China Sea makes sense in the future.” Thomas noted that Chinese capabilities in the region currently outmatch those of its neighbors, and therefore Southeast Asian nations see Japan as a stabilizing force.

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The United States has also increased its calls for China to stop its reclamation projects in the South China Sea.

Japanese Prime Minister Shinzo Abe is currently trying to pass legislation that would give the JSDF the right to engage in “collective self-defense.” This would significantly reduce the legal barriers inhibiting Japan’s ability to play a military role in the South China Sea dispute.

Zachary Keck is managing editor of The National Interest. You can find him on Twitter: @ZacharyKeck.