Stability in the Taiwan Strait is more important than ever, threatened by increasing Chinese military pressure, Japan's annual defense report said Tuesday, touching on the issue for the first time.

This year's white paper, reported to the Cabinet the same day, said China has further intensified military activities around Taiwan with some 380 Chinese warplanes entering Taiwan's southwestern airspace in 2020, citing data from the island's Defense Ministry.

Supplied photo shows the cover of Japan's 2021 defense white paper. (Photo courtesy of the Defense Ministry)(Kyodo)

The paper also mentioned that Chinese warships, including an aircraft carrier, sailed through the Bashi Channel, the waterway connecting the South China Sea with the western Pacific Ocean, and conducted a military drill last year.

"Stabilizing the situation surrounding Taiwan is important for Japan's security and the stability of the international community," the paper said.

"With military activities in the East and South China seas and around Taiwan becoming more active, we need to pay more attention to the military trends of the two countries (the United States and China) in the Indo-Pacific region," Defense Minister Nobuo Kishi said at a press conference when asked why Taiwan stability was mentioned in the report.

As attention was growing to the timeline of a possible Chinese invasion of the island democracy, former U.S. Indo-Pacific Command chief Adm. Philip Davidson said in March that China could try to invade Taiwan "in the next six years."

Japanese Prime Minister Yoshihide Suga and U.S. President Joe Biden said in a joint statement in April that peace and stability are important across the strait, the first reference to Taiwan by the two countries' leaders in such a document in more than half a century.

Taiwan and mainland China have been governed separately since they split amid a civil war in 1949. Beijing has since regarded Taiwan as a renegade province awaiting reunification by force if necessary.

While pledging to build up his nation's military, Chinese President Xi Jinping committed to the "reunification" of Taiwan with the mainland in a speech on the 100th anniversary of the ruling Communist Party's founding.

Japanese Defense Minister Nobuo Kishi holds up this year's defense white paper at a press conference in Tokyo on July 13, 2021. (Kyodo)

In reaction to the release of the paper, Chinese Foreign Ministry spokesman Zhao Lijian told reporters, "China is strongly dissatisfied with and firmly opposes" the report.

Japan has "grossly interfered" in China's internal affairs, "unreasonably condemned" China's normal defense and military activities and "exaggerated the so-called Chinese threat," Zhao said.

Kishi wrote the preface for the paper in a rare move, saying Japan would collaborate with such countries as Australia, Britain, Canada, France, Germany, India, New Zealand and the United States that share the same value to promote a free and open Indo-Pacific, an initiative apparently aimed at countering China's rising assertiveness.

"It expresses my determination as defense minister to protect the country, including values" such as freedom, democracy, the rule of law and respect for fundamental human rights, Kishi said at the press conference.

The Taiwan issue was raised in the white paper to show that concerns voiced in the Japan-U.S. leaders' communique remain intact, said Takeshi Yuzawa, a professor of international relations of East Asia at Hosei University.

"Japan's intention is also reflected to show its increasingly serious concerns over China's military activity against Taiwan," he said.

The paper gives harsher criticism for China's "unilateral attempts to change the status quo by coercion" near the Japanese-controlled Senkaku Islands in the East China Sea.

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

Last year, Chinese coast guard vessels were spotted near the islands for 111 consecutive days, the longest streak since Japan bought the islets from a private owner and put them under state control in 2012. The paper claims activities of Chinese vessels represent "a violation of international law."

Beijing implemented a maritime law in February that allows its coast guard to use weapons against foreign vessels it views as illegally entering its waters.

The law "includes problematic provisions in terms of inconsistency with international law," the paper said.

The paper includes a new section focusing on U.S.-China relations, describing the world's two biggest economies as being in a "strategic race" and saying their rivalry will be even more apparent in various fields.

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