The waterway, the Tumen River, flows east along the border of China and North Korea, and eventually also of Russia, before emptying into the Sea of Japan.

Chinese vessels can currently only freely navigate the river until the village of Fangchuan, on the eastern end of landlocked Jilin province. Permission is required from both Russia and North Korea to navigate the remaining 15-kilometer stretch to the Sea of Japan. A Soviet-era, 7-meter-tall bridge also blocks the passage of larger vessels.

Chinese President Xi Jinping and Russian President Vladimir Putin included in a joint statement following a summit last month a mention that the countries will engage in a “constructive dialogue” with North Korea about the Tumen River.

China historically held the area until the Russian Empire took control in the 1860s. China has repeatedly urged Russia and North Korea to allow Chinese vessels to navigate the river to the Sea of Japan, proposing the creation of a special economic zone along its banks.

Russia used to be reluctant on the idea, concerned that it would increase China’s influence in Northeast Asia. But its attitude is changing as the power dynamic between Moscow, Beijing and Pyongyang shifts.

Russia has grown increasingly dependent on China for trade amid Western sanctions over its invasion of Ukraine in 2022. Energy exports to China have increased since the start of the Ukraine war. Moscow also relies on China for electronic components and automobiles, and imports from China increased to 37% of the total in 2023 from 22% before the war.

Sanctions have also brought Russia and North Korea closer together. North Korea has supplied artillery shells and other weaponry to Russia.

Zhao Leji, who ranks third in the Chinese Communist Party hierarchy, met with North Korean leader Kim Jong Un in Pyongyang in April.

North Korea will likely agree to engage in talks regarding the Tumen River, according to Wang Wen, executive dean of the Chongyang Institute for Financial Studies at the Renmin University of China. Wang advocated for Chinese vessels to be able to navigate the river at the Eastern Economic Forum in Vladivostok, Russia, last year.

China is considering widening the Tumen in its lower reaches and demolishing the bridge with Russian and North Korean approval. Allowing larger vessels to navigate through “will facilitate the cheaper transport of Chinese supplies by sea and promote economic exchanges with northeastern Asia, including Japan and South Korea,” Wang said.

The change could also significantly affect security in the region.

Chisako Masuo, a professor researching Chinese foreign policy at Kyushu University in Fukuoka, Japan, said the larger vessels China hopes to navigate directly to the Sea of Japan include coast guard patrol ships.

The Japan Coast Guard is currently scrambling to keep up with increased activity by Chinese government vessels in waters near the Japan-administered Senkaku Islands, claimed by China as the Diaoyu. On Friday, four China Coast Guard ships equipped with what appeared to be machine guns had apparently entered Japan’s territorial waters at around the same time.

“If China Coast Guard ships become active in the Sea of Japan, Japan will need to divert its own coast guard vessels that are currently monitoring waters near the Senkaku Islands,” Masuo said.

“It could weaken monitoring in the East China Sea,” she said.

Xi and Putin’s joint statement also outlined plans for expanded joint military drills and joint sea and air patrols.

Chinese and Russian forces have engaged in joint maritime and air drills in the Sea of Japan. An increased presence by the China Coast Guard, which essentially functions as a second navy, could expand the scope of such activities in the area.