Serious border demarcation negotiations did not occur until shortly before the end of the Soviet Union in 1991. In particular, both sides agreed that
Damansky/Zhenbao Island belonged to China. (Both sides claimed the island was under their control at the time of the agreement.) On October 17, 1995, an agreement over the last 54 kilometres (34 mi) stretch of the border was reached, but the question of control over three islands in the Amur and Argun rivers was left to be settled later.
In a border agreement between Russia and China signed on October 14, 2004, that dispute was finally resolved. China was granted control over Tarabarov Island (Yinlong Island),
Zhenbao Island, and approximately 50% of Bolshoy Ussuriysky Island (Heixiazi Island), near Khabarovsk. China's Standing Committee of the National People's Congress ratified this agreement on April 27, 2005, with the Russian Duma following suit on May 20. On June 2, Chinese Foreign Minister Li Zhaoxing and Russian Minister of Foreign Affairs Sergei Lavrov exchanged the ratification documents from their respective
On July 21, 2008, Chinese Foreign Minister Yang Jiechi and his Russian counterpart, Sergei Lavrov, signed an additional Sino-Russian Border Line Agreement marking the acceptance of the demarcation the eastern portion of the Chinese-Russian border in Beijing, China. An additional protocol with a map affiliated on the eastern part of the borders both countries share was signed. The agreement also includes the return of Yinlong/Tarabarov Island and half of Heixiazi/Bolshoi Ussuriysky
to a Chinese blogger in September 1997, China and Russia in the case of mutual concessions,
were in the final completion of demarcation negotiations. The largest
discussion theme between the two sides was regarding the mouth of the Tumen River area
at Khassan. Russia had promissed China access to the Sea of Japan at the
lake southwest of the Russian town of Kraskino, but in the middle of the
1990s the Primorsky Duma denied any border change because "it was not
in the interest of the Russian Federation". The Chinese side from the overall situation of Sino-Russian relations, agreed to make some
adjustments – Russia should handed back Sakhalinsky Island to China as compensation. In early November 1997, the third time in President Boris Yeltsin during his visit, China and Russia issued a joint communique that the leaders of demarcation work completed on schedule.
Sakhalinsky Island had become a part of China. 3)