China – which views the self-ruled island as its own sovereign territory – protested the negotiations, saying they infringe on its sovereignty.

The effort was launched on Saturday by China's Ministry of Transport in coordination with the local authorities, according to Xinhua. The operation is aimed at fully exercising China's maritime administrative law enforcement jurisdiction and safeguarding national rights and interests, the report said.

The operation follows a May 28 summit in Tokyo in which Japanese Prime Minister Sanae Takaichi and Philippines President Ferdinand Marcos Jr. issued a joint statement announcing the start of maritime delimitation talks on their respective exclusive economic zones and continental shelves.

Chinese Foreign Ministry spokeswoman Mao Ning denounced the announcement, saying the waters Japan and the Philippines intend to delimit lie east of Taiwan, which Beijing claims as an exclusive economic zone.

"Any negotiations involving maritime delimitation in waters east of Taiwan must involve China," Mao said, adding that Japan and the Philippines violated international law by bypassing Beijing.

Taiwan has also sounded the alarm over the imminent talks, urging Tokyo and Manila to consult with it, as the area likely to be subject to negotiations overlaps with waters in which the island claims "rights and interests."

Japanese Chief Cabinet Secretary Minoru Kihara said, however, that any agreement reached between Japan and the Philippines "would not be legally binding on any third party."

Taiwan's coast guard said it deployed at least five vessels "to respond appropriately" to the Chinese operation, which it said violates international law, and monitored four Chinese government vessels departing from the Port of Xiamen on the mainland.

China regards Taiwan as its own territory, and President Xi Jinping has refused to rule out the use of force to achieve reunification.

Tensions between China and Japan over Taiwan have simmered since November 2025, when Prime Minister Takaichi warned that a Chinese attempt to take over the island could be grounds for a military intervention. China subsequently accused Takaichi of being the first Japanese prime minister to explicitly frame a Taiwan scenario as a "survival-threatening situation," adding that the narrative has historically served as "a go-to tactic for Japanese militarism to launch aggression."