Tokyo CNN  — 

Japan is drawing a red line around an island chain also claimed by China, pushing back at Beijing’s increasingly aggressive military posturing, and setting the stage for a potential showdown between the region’s two biggest powers.

In an exclusive interview with CNN, Japanese Defense Minister Nobuo Kishi said the Senkaku Islands, known as the Diaoyu Islands in China, are unquestionably Japanese territory and would be defended as such, with Tokyo matching any Chinese threat to the islands ship for ship, and beyond if necessary.

Japan has been expanding its Self-Defense Forces, adding state-of-the-art F-35 fighter jets and converting warships to aircraft carriers for them. It is also building new destroyers, submarines and missiles, all the while noting its military expenditure still pales in comparison with China’s increased military spending.

“Against Chinese action to Senkaku Islands and other parts of the East China Sea … we have to demonstrate that the government of Japan is resolutely defending our territory with the greater number of Japanese coast guard vessels than that of China,” Kishi said. “There is no territorial dispute relating to the Senkaku Islands between Japan and other countries,” he added.

Tensions over the uninhabited rocky chain – 1,200 miles (1,900 kilometers) southwest of Tokyo but only a third of that distance from Shanghai – have simmered for years, and claims over them date back centuries.

When tensions spiked over the islands in 2012, it sparked a groundswell of nationalist sentiment in China. Public protests broke out in dozens of Chinese cities, with Japanese-branded cars smashed, Japanese stores and restaurants vandalized, and debris hurled at the Japanese Embassy in Beijing.

At the governmental level, China has been just as strident as Kishi is in claiming the island chain.

Minamikojima, Kitakojima and Uotsuri islands, part of the five main islands in the Senkaku group in the East China Sea, on September 11, 2013.

“The Diaoyu Island and its affiliated islands are an inherent part of China’s territory, and it is our inherent right to carry out patrols and law enforcement activities in these waters,” China’s Foreign Ministry said in a statement last year.

China has been backing its claims in the region with its ships, and by establishing new laws that give its coast guard expanded powers.

According to Japanese authorities, Chinese Coast Guard vessels have ventured into Japanese territorial waters, or within 12 nautical miles of Japanese land, a total of 88 times between January 1 and the end of August. While in the contiguous zone, waters between islands but not within 12 miles of shore, there have been 851 Chinese incursions.

Experts say China’s strategy is to put its forces in places in and around contested areas and exert Beijing’s law and authority over them. Such action makes the Chinese claims seem like due course.

“Exercising coastal state rights is an important step in corroborating sovereignty through practice,” said Alessio Patalano, professor of war and strategy at King’s College in London.

Kishi has taken notice.

China Marine Surveillance vessels (front and middle) cruise with a Japan Coast Guard ship near Kitakojima and Minamikojima of the disputed Senkaku Islands on April 23, 2013.

“There are actions that continue to challenge an integral part of Japan’s sovereign territory. These actions are making it a fait accompli,” he said.

That “integral” Japanese territory extends even closer to another possible flashpoint in the Japan-China relationship.

Taiwan’s importance to Japan

Japan’s westernmost island is at the very end of a string of Japanese possessions paralleling the Chinese coast and extending south some 700 miles (1,125 kilometers) from the main island of Kyushu, through the military hub of Okinawa and the resort island of Ishigaki, to the tiny island of Yonaguni.

With its 11 square miles of rock and population of fewer than 2,000 people, Yonaguni sits only 68 miles (110 kilometers) from Taiwan, the democratically governed island over which Beijing claims sovereignty.

Taiwan and mainland China have been governed separately since the end of a civil war more than seven decades ago.