The government lodged a protest with the Chinese Embassy in Tokyo after discovering that China had unilaterally started construction of a suspected drilling rig to develop gas fields in disputed waters in the East China Sea.

A bilateral agreement was reached in 2008 to jointly develop gas fields in the area, but talks on crucial aspects of the joint development, such as the boundary of the exclusive economic zone and continental shelf, remain stalled.

The Foreign Ministry said it confirmed that Beijing is building a structure for drilling on its side near the median line of the two countries.

“It is extremely regrettable that China is pursuing the development unilaterally and Japan cannot accept it,” Prime Minister Fumio Kishida said during a visit to Kyoto on May 21.

He said Japan has strongly urged China to swiftly resume talks on joint development of the natural gas resources.

Officials said 16 drilling rigs already stand close to the de facto maritime border with Japan.

Commenting on other issues, Kishida expressed hopes that his summit talks with U.S. President Joe Biden on May 23 will result in a candid exchange of opinions over a string of shared challenges, such as security and the war in Ukraine.

He also said the two leaders will reaffirm to work closely to achieve a free and open Indo-Pacific region.