China's borders have more than of land frontier shared with nearly all the nations of mainland East Asia, and have been disputed at a number of points. In the western sector, China claimed portions of the Pamir Mountains area, a region of soaring mountain peaks and glacier-filled valleys where the borders of Afghanistan, Pakistan, the former Soviet Union, and China meet in Central Asia. North and east of this region, some sections of the border remained undemarcated in 1987. The frontier with the Soviet Union has been a source of continual friction. In 1954 China published maps showing substantial portions of Soviet Siberian territory as its own. In the northeast, border friction with the Soviet Union produced a tense situation in remote regions of Inner Mongolia and Heilongjiang along segments of the Argun River, Amur River, and Ussuri River. Each side had massed troops and had exchanged charges of border provocation in this area. In a September 1986 speech in Vladivostok, the Soviet leader Mikhail Gorbachev offered the Chinese a more conciliatory position on Sino-Soviet border issues. In 1987 the two sides resumed border talks that had been broken off after the 1979 Soviet invasion of Afghanistan (see Sino-Soviet relations). Although the border issue remained unresolved as of late 1987, China and the Soviet Union agreed to consider the northeastern sector first. In October 2004, China signed an agreement with Russia on the delimitation of their entire -long border, which had long been in dispute.