TOKYO -- If China invades Taiwan, Tokyo may interpret the move as a "threat to Japan's survival" and deploy the Self-Defense Forces to exercise collective self-defense, Deputy Prime Minister Taro Aso said Monday.

"If a major incident happened [in Taiwan], it would not be strange at all if it touches on a situation threatening survival," Aso said during a speech in Tokyo. "If that is the case, Japan and the U.S. must defend Taiwan together."

Aso, who also serves as finance minister, is one of four cabinet members who sit on Japan's National Security Council.

Japan's deputy prime minister noted that "the situation over Taiwan is becoming extremely intense," referring to Chinese President Xi Jinping's comments about the self-ruled island during a speech last week to commemorate the Communist Party's 100-year anniversary.

"Resolving the Taiwan question and realizing China's complete reunification is a historic mission and an unshakable commitment" of the party, Xi said Thursday.

Japan's Deputy Prime Minister Taro Aso speaks in Tokyo on July 5. (Photo by Kaoru Osawa)

Given Japan's constitutional restrictions on the use of its armed forces, Tokyo is authorized to mobilize the SDF only for national defense. Previously, the only scenario in which the SDF could use force involved an "armed attack situation," such as an organized and premeditated attack against Japan's territorial land, sea or airspace.

In 2015, under then-Prime Minister Shinzo Abe, Japan enacted a series of security laws that expanded the conditions for deploying the SDF. One new concept involved situations threatening Japan's survival.

In a paper titled " Japan's Potential Contributions in an East China Sea Contingency ," RAND Corp. political scientist Jeffrey Hornung said this new concept means Japan does not have to be directly attacked.

"For example, since the United States is responsible for defending Japan under Article 5 of the security treaty, if the United States is attacked, this could affect Japan's survival and thus can be defined as such," Hornung wrote. "In turn, this enables Japan to use force as the exercise of collective self-defense."