"The most important thing now is to make sure that war doesn't break out in the Taiwan Strait," Aso, vice president of Japan's ruling Liberal Democratic Party, said in a speech in Taipei during a three-day visit to Taiwan.

"I believe that now is the time for Japan, Taiwan, the United States and other like-minded countries to be prepared to put into action very strong deterrence," he said in remarks streamed online. "It's the resolve to fight."

He added that clearly showing the will to defend Taiwan was a form of deterrence. He did not specify China as the aggressor, but said it was crucial for Japan, as a neighbour of Taiwan, and other countries that are upholding international order, to send the message to China and the rest of the international community.

Aso is the most senior Japanese political official to visit Taiwan since 1972.

China views democratically governed Taiwan as its own territory and has never ruled out the use of force to bring the island under its control. Taiwan's government strongly rejects China's sovereignty claims.

Speaking before Aso at the same forum, Taiwan President Tsai Ing-wen said her government was committed to improving its defences and did not take the backing of its security partners for granted.

"While we don't seek military confrontation and hope for a peaceful, stable and beneficial coexistence with our neighbours, Taiwan is always ready to defend our democracy and way of life," she said.

Tensions over Taiwan have contributed to a decision by close U.S. ally Japan to boost its defence spending.

In 2021, Aso, then deputy prime minister, called any invasion of Taiwan by China a "threat to Japan's survival" and said Japan and the U.S. would defend Taiwan together should such an incident happen.

Those comments angered China, which said the remarks "harmed the political foundation of China-Japan relations."

Aso is scheduled to meet Tsai on Tuesday afternoon at the presidential office.