Although tensions have eased and the leaders of both sides have taken a more conciliatory stance, the border issue has still not been resolved. Despite their view that previous border treaties were unequal, China`s leaders were willing to negotiate on the basis of modern borders. This left about 35,000 km² of territory in dispute, including about 28,000 km² in the Pamir Mountains of Tajikistan, 6,000 km² elsewhere along the western border and about 1,000 km² along the Argun, Amur and Ussuri rivers on the eastern border.  Border negotiations finally resumed in 1987 at the initiative of Mikhail Gorbachev. On 16 May 1991, a few months before the final dissolution of the USSR, an agreement was reached on the eastern part of the border. Russia inherited most of the former Sino-Soviet border and ratified the agreement in February 1992, while the other post-Soviet republics negotiated separate border agreements. In the last years of the Soviet Union, tensions on the then heavily fortified Sino-Soviet border decreased. In 1990/91, the two countries agreed to significantly reduce their forces stationed along the border.  To date, many abandoned military installations are in Russia`s border districts.  The Sino-Soviet border dispute began with the Cossack-Manchu (Qing Dynasty) wars in the 1670s-80s over a Cossack colony on Amur. The resolution process began in the early 1980s, when Moscow abandoned its “escalation strategy.” China responded positively by suggesting that “persistent” problems should not stop the solution in other sectors or should be “angry”. In December 1988, Deng Xiaoping Rajiv Gandhi made the same proposal to usher in an “Asian century”.
The much shorter western border section (less than 100 kilometers (62 miles)) lies between the Russian Altai Republic and China`s Xinjiang. It takes place in the mostly snow-capped high-altitude region of the Altai Mountains. Its western terminus is the China-Kazakhstan-Russia tri-border zone, whose location is defined by the trilateral agreement as 49°06′54″N 87°17′12″E / 49.11500°N 87.28667°E / 49.11500; 87.28667, elevation, 3327 m. Its eastern end is the Sino-Mongolian-Russian western border triangle, atop The Tavan Bogd Uul Summit (Mt Kuitun), at coordinates 49°10′13.5″N 87°48′56.3″E / 49.170417°N 87.815639°E / 49.170417; 87.815639. Menkeseli was a 7.5 km² (7 mi²) area along the Argun River that should have been transferred to China under the agreement. However, this was rejected by local Russian civilians who used this area for fishing. The dispute was finally concluded in 1996, in which the region was transferred to China, but local Russian residents were guaranteed special rights of use in the region. The Sino-Soviet border dispute proves that a show of force is unlikely to deter the Chinese. China did not bow even during internal conflicts or when the Soviet Union alluded to nuclear strikes. By all accounts, the same policy seems to be practiced by Xi Jinping.
The 1991 Sino-Soviet border agreement was a treaty between China and the Soviet Union that established a demarcation work to resolve most border disputes between the two states. Originally signed by China and the Soviet Union, the terms of the agreement were taken over by Russia after the dissolution of the Soviet Union. The treaty resulted in some minor territorial changes along the border. The seventeenth and eighteenth centuries marked a period of peace for the border. Over the next century, however, an expanding Russia and a weakened China exacerbated tensions. Through a series of “unequal treaties,” the Russian Empire acquired massive tracts of sparsely populated land from the trouble-stricken Qing Dynasty. Above all, the Beijing Convention (1860) saw the bloodless transfer of 600,000 square miles of Qing territory to the Russian Empire in Northeast Asia, moving the border south to its current location. At a time when the Soviet Union showed signs of tension, bilateral and border relations improved considerably. In 1991, the two countries reviewed and marked their border in the Sino-Soviet border agreement, and in 2004, the Chinese renounced any historical claims to the region in exchange for recognizing sovereignty over some disputed islands. Geopolitically, the newly independent Central Asian countries also served as a buffer zone between the two giants. As with many other international borders, there is a bilateral treaty on the physical modalities of the administration of the Sino-Russian border.
The agreement in force today was signed in Beijing in 2006.  According to the Russian Border Authority, there were 26 border crossings at the Sino-Russian border as of October 1, 2013; all are located in the eastern part of the border. Twenty-five of them are provided for in the bilateral agreement of 27 January 1994, and another is determined by an additional special decree issued by the Russian Government. The 25 border crossings established by the treaty include four railway crossings (at one of them, at Tongjiang/Nizhneleninskoye, the railway bridge is still under construction), eleven as motorway crossings, one as a river crossing and nine as “mixed” (mainly ferry crossings).   The Sino-Russian border consists of two separate non-contiguous sections: the long eastern section between Mongolia and North Korea and the much shorter western section between Kazakhstan and Mongolia. Since the islands of the Argun, Amur and Ussuri rivers often divide the rivers into several streams, the location of the main current (and therefore the border) was often not immediately apparent. Obviously, each country would receive a greater number of islands if the recognized main channel were closer to the opposite shore. Thus, demarcation work was often controversial and was the subject of local protests in disputed areas. The demarcation work lasted almost until 1997. Today`s Sino-Russian border is largely inherited from Russia (with minor adjustments) from the Soviet Union, while the Sino-Soviet border line was essentially the same as the border between the Russian and Qing empires, established by a series of treaties from the 17th to the 19th century.
Border issues first became an issue after Russia`s rapid expansion into Siberia in the 17th century, with skirmishes between them and Qing China at times.  Below is a list of important border treaties, noting which section of the current Sino-Russian border was largely determined by them: Since the collapse of the Soviet Union, Russia has experienced a mass exodus of the population of the entire Far Eastern Federal District, from 9 million in 1991 to 6.2 million in 2010 . . . .