A Chinese invasion of Taiwan could be an "existential threat" to Japan that would lead to a collective defence of the democratic island with the United States, Japan's deputy prime minister said

Taro Aso, who also serves as finance minister, made the remarks at a fundraising event in Tokyo on Monday, according to a report by Japan's Jiji Press.

"If a major incident occurs in Taiwan, it's not at all unusual to consider it an existential threat [to Japan]," the senior official was quoted as saying. "In such a case, Japan and the United States will have to work together to defend Taiwan."

Observers have noted the finesse with which Japanese officials conduct diplomacy, including their careful use of words. The deputy PM's description of an "existential threat" is a choice phrase required to trigger the relevant self-defence clauses in Japan's otherwise pacifist constitution.

Aso, who is on Japan's presidential-style National Security Council, explained his thinking by warning "Okinawa could be next" after an invasion of Taiwan by China. Japan "could exercise its right to collective self-defence in a limited way," he said at the event.

Asked about his remarks on Tuesday, Aso reportedly responded: "We are closely monitoring the situation."

Japan's outlying island of Yonaguni lies less than 70 miles off Taiwan's east coast, while the disputed Senkaku Islands are about 120 miles northeast of Taipei. Both are administered under Japan's Okinawa Prefecture.

China claims the Senkaku islets through its claim to Taiwan. Both Beijing and Taipei list the island chain as part of Taiwan's eastern county of Yilan, but the Taiwanese government has been less assertive about its claim over the East China Sea areas in recent years. The Chinese government claims democratically ruled Taiwan is a province waiting to be "unified" with the mainland. Taiwan says it's a sovereign state by the name of the Republic of China.

In a recent address marking the Chinese Communist Party's (CCP) 100-year anniversary, China's Xi Jinping described the party's ambition to "resolve the Taiwan question" as a "historic mission."

"No one should underestimate the great resolve, the strong will and the extraordinary capability of the Chinese people to defend their national sovereignty and territorial integrity," he declared in Beijing to loud applause.

China has pledged never to renounce the use of force against Taiwan. This policy position was formalized in the Anti-Secession Law of 2005, which articulates the conditions for the use of "non-peaceful means" to capture the island, which the People's Republic of China has never governed.

Tokyo established formal relations with Beijing in 1972, seven years before Washington also switched allegiances from Taipei.

As part of the diplomatic agreement, the Japanese government expressed its "understanding" and "respect" for China's position that Taiwan is part of its territory. Tokyo has maintained this position while insisting on its informal relations with Taipei through non-official channels.

Like the U.S. "one-China" policy, which "acknowledges" but does not recognize or affirm the Chinese position, the ambiguous posture leaves wiggle room for a spectrum of interactions with Taiwan. With China's escalating military pressure on Taiwan as well as Japan in recent years, officials in Tokyo have become increasingly vocal about the need to prevent conflict in the Taiwan Strait.

Prospect of Attack By China

At an event hosted by the Hudson Institute think tank on June 28, Japan's Deputy Defence Minister Yasuhide Nakayama said Tokyo and Washington needed to "wake up" to the prospect of an attack by China.

"We have to protect Taiwan as a democratic country," he said during the discussion, drawing protests from China's Foreign Ministry the following day.

It was the second time last month a high-ranking Japanese official had mentioned Taiwan in those terms, after Yoshihide Suga angered Beijing by calling Taiwan a country during a National Diet session on June 9.

Analysts say Japan's ruling Liberal Democratic Party may be riding a wave of pro-Taiwan sentiment among the public ahead of the country's October general election.

Ian Easton, senior director at the Project 2049 Institute, says Chinese leader Xi is "especially keen on annexing Taiwan and has ordered the [People's Liberation Army] to undertake a campaign of coercion" against it.

It has "destabilized the security situation in the Taiwan Strait and heightened tensions with the United States and its allies," Easton told Newsweek ahead of the Communist Party centennial on July 1.

Some argue that Xi, who is expected to be re-elected for an unprecedented third term next year, may take an increasingly hawkish stance on Taiwan to secure his leadership position.

Easton says this is open to interpretation, but added: "In any event, it would seem prudent for President Biden and his foreign policy team to assume the continuance of aggressive CCP behaviour across all domains and plan for the worst."